@article {2022|2156, title = {Building Biological Relevance Into Integrative Modelling of Macromolecular Assemblies}, journal = {Frontiers in Molecular Biosciences}, volume = {9}, year = {2022}, pages = {826136}, abstract = {

Recent advances in structural biophysics and integrative modelling methods now allow us to decipher the structures of large macromolecular assemblies. Understanding the dynamics and mechanisms involved in their biological function requires rigorous integration of all available data. We have developed a complete modelling pipeline that includes analyses to extract biologically significant information by consistently combining automated and interactive human-guided steps. We illustrate this idea with two examples. First, we describe the ryanodine receptor, an ion channel that controls ion flux across the cell membrane through transitions between open and closed states. The conformational changes associated with the transitions are small compared to the considerable system size of the receptor; it is challenging to consistently track these states with the available cryo-EM structures. The second example involves homologous recombination, in which long filaments of a recombinase protein and DNA catalyse the exchange of homologous DNA strands to reliably repair DNA double-strand breaks. The nucleoprotein filament reaction intermediates in this process are short-lived and heterogeneous, making their structures particularly elusive. The pipeline we describe, which incorporates experimental and theoretical knowledge combined with state-of-the-art interactive and immersive modelling tools, can help overcome these challenges. In both examples, we point to new insights into biological processes that arise from such interdisciplinary approaches.

}, issn = {2296-889X}, doi = {10.3389/fmolb.2022.826136}, url = {https://www.frontiersin.org/article/10.3389/fmolb.2022.826136}, author = {Molza, Anne-Elisabeth and Westermaier, Yvonne and Moutte, Magali and Ducrot, Pierre and Danilowicz, Claudia and Godoy-Carter, Veronica and Prentiss, Mara and Robert, Charles H. and Marc Baaden and Pr{\'e}vost, Chantal} } @article {2022|2150, title = {Modeling the Dynamics of Protein-Protein Interfaces, How and Why?}, journal = {Molecules}, volume = {27}, year = {2022}, pages = {1841}, abstract = {

Protein-protein assemblies act as a key component in numerous cellular processes. Their accurate modeling at the atomic level remains a challenge for structural biology. To address this challenge, several docking and a handful of deep learning methodologies focus on modeling protein-protein interfaces. Although the outcome of these methods has been assessed using static reference structures, more and more data point to the fact that the interaction stability and specificity is encoded in the dynamics of these interfaces. Therefore, this dynamics information must be taken into account when modeling and assessing protein interactions at the atomistic scale. Expanding on this, our review initially focuses on the recent computational strategies aiming at investigating protein-protein interfaces in a dynamic fashion using enhanced sampling, multi-scale modeling, and experimental data integration. Then, we discuss how interface dynamics report on the function of protein assemblies in globular complexes, in fuzzy complexes containing intrinsically disordered proteins, as well as in active complexes, where chemical reactions take place across the protein-protein interface.

}, issn = {1420-3049}, doi = {10.3390/molecules27061841}, url = {https://www.mdpi.com/1420-3049/27/6/1841}, author = {Karaca, Ezgi and Pr{\'e}vost, Chantal and S Sacquin-Mora} } @article {2021, title = {Moving pictures: Reassessing docking experiments with a dynamic view of protein interfaces.}, journal = {Proteins}, year = {2021}, month = {2021 May 26}, abstract = {

The modeling of protein assemblies at the atomic level remains a central issue in structural biology, as protein interactions play a key role in numerous cellular processes. This problem is traditionally addressed using docking tools, where the quality of the models is based on their similarity to a single reference experimental structure. However, using a static reference does not take into account the dynamic quality of the protein interface. Here, we used all-atom classical Molecular Dynamics simulations to investigate the stability of the reference interface for three complexes that previously served as targets in the CAPRI competition. For each one of these targets, we also ran MD simulations for ten models that are distributed over the High, Medium and Acceptable accuracy categories. To assess the quality of these models from a dynamic perspective, we set up new criteria which take into account the stability of the reference experimental protein interface. We show that, when the protein interfaces are allowed to evolve along time, the original ranking based on the static CAPRI criteria no longer holds as over 50\% of the docking models undergo a category change (which can be either toward a better or a lower accuracy group) when reassessing their quality using dynamic information.

}, issn = {1097-0134}, doi = {10.1002/prot.26152}, author = {Chantal Pr{\'e}vost and S Sacquin-Mora} } @article {2021|2146, title = {When Order Meets Disorder: Modeling and Function of the Protein Interface in Fuzzy Complexes}, journal = {Biomolecules}, volume = {11}, year = {2021}, pages = {1529}, abstract = {

The degree of proteins structural organization ranges from highly structured, compact folding to intrinsic disorder, where each degree of self-organization corresponds to specific functions: well-organized structural motifs in enzymes offer a proper environment for precisely positioned functional groups to participate in catalytic reactions; at the other end of the self-organization spectrum, intrinsically disordered proteins act as binding hubs via the formation of multiple, transient and often non-specific interactions. This review focusses on cases where structurally organized proteins or domains associate with highly disordered protein chains, leading to the formation of interfaces with varying degrees of fuzziness. We present a review of the computational methods developed to provide us with information on such fuzzy interfaces, and how they integrate experimental information. The discussion focusses on two specific cases, microtubules and homologous recombination nucleoprotein filaments, where a network of intrinsically disordered tails exerts regulatory function in recruiting partner macromolecules, proteins or DNA and tuning the atomic level association. Notably, we show how computational approaches such as molecular dynamics simulations can bring new knowledge to help bridging the gap between experimental analysis, that mostly concerns ensemble properties, and the behavior of individual disordered protein chains that contribute to regulation functions.

}, issn = {2218-273X}, doi = {10.3390/biom11101529}, url = {https://www.mdpi.com/2218-273X/11/10/1529}, author = {S Sacquin-Mora and Chantal Pr{\'e}vost} } @article {2019|2062, title = {The positioning of Chi sites allows the RecBCD pathway to suppress some genomic rearrangements}, journal = {Nucleic Acids Res}, volume = {47}, year = {2019}, month = {02}, pages = {1836-1846}, abstract = {

Bacterial recombinational repair of double-strand breaks often begins with creation of initiating 3\&$\#$39; single-stranded DNA (ssDNA) tails on each side of a double-strand break (DSB). Importantly, if the RecBCD pathway is followed, RecBCD creates a gap between the sequences at 3\&$\#$39; ends of the initiating strands. The gap flanks the DSB and extends at least to the nearest Chi site on each strand. Once the initiating strands form ssDNA-RecA filaments, each ssDNA-RecA filament searches for homologous double-stranded DNA (dsDNA) to use as a template for the DNA synthesis needed to fill the gap created by RecBCD. Our experimental results show that the DNA synthesis requires formation of a heteroduplex dsDNA that pairs \>20 contiguous bases in the initiating strand with sequence matched bases in a strand from the original dsDNA. To trigger synthesis, the heteroduplex must be near the 3\&$\#$39; end of the initiating strand. Those experimentally determined requirements for synthesis combined with the Chi site dependence of the function of RecBCD and the distribution of Chi sites in bacterial genomes could allow the RecBCD pathway to avoid some genomic rearrangements arising from directly induced DSBs; however, the same three factors could promote other rearrangements.

}, doi = {10.1093/nar/gky1252}, author = {Li, Chastity and Danilowicz, Claudia and Tashjian, Tommy F and Godoy, Veronica G and Chantal Pr{\'e}vost and Prentiss, Mara} } @article {2019|2063, title = {Residues in the fingers domain of the translesion DNA polymerase DinB enable its unique participation in error-prone double-strand break repair}, journal = {J Biol Chem}, volume = {294}, year = {2019}, month = {May}, pages = {7588-7600}, abstract = {

The evolutionarily conserved Escherichia coli translesion DNA polymerase IV (DinB) is one of three enzymes that can bypass potentially deadly DNA lesions on the template strand during DNA replication. Remarkably, however, DinB is the only known translesion DNA polymerase active in RecA-mediated strand exchange during error-prone double-strand break repair. In this process, a single-stranded DNA (ssDNA)-RecA nucleoprotein filament invades homologous dsDNA, pairing the ssDNA with the complementary strand in the dsDNA. When exchange reaches the 3\&$\#$39; end of the ssDNA, a DNA polymerase can add nucleotides onto the end, using one strand of dsDNA as a template and displacing the other. It is unknown what makes DinB uniquely capable of participating in this reaction. To explore this topic, we performed molecular modeling of DinB\&$\#$39;s interactions with the RecA filament during strand exchange, identifying key contacts made with residues in the DinB fingers domain. These residues are highly conserved in DinB, but not in other translesion DNA polymerases. Using a novel FRET-based assay, we found that DinB variants with mutations in these conserved residues are less effective at stabilizing RecA-mediated strand exchange than native DinB. Furthermore, these variants are specifically deficient in strand displacement in the absence of RecA filament. We propose that the amino acid patch of highly conserved residues in DinB-like proteins provides a mechanistic explanation for DinB\&$\#$39;s function in strand exchange and improves our understanding of recombination by providing evidence that RecA plays a role in facilitating DinB\&$\#$39;s activity during strand exchange.

}, keywords = {DinB, DNA damage, DNA polymerase, DNA polymerase IV, DNA repair, DNA synthesis, homologous recombination, RecA}, doi = {10.1074/jbc.RA118.006233}, author = {Tashjian, Tommy F and Danilowicz, Claudia and Molza, Anne-Elizabeth and Nguyen, Brian H and Chantal Pr{\'e}vost and Prentiss, Mara and Godoy, Veronica G} } @article {2019|2064, title = {Slow extension of the invading DNA strand in a D-loop formed by RecA-mediated homologous recombination may enhance recognition of DNA homology}, journal = {J Biol Chem}, volume = {294}, year = {2019}, month = {May}, pages = {8606-8616}, abstract = {

DNA recombination resulting from RecA-mediated strand exchange aided by RecBCD proteins often enables accurate repair of DNA double-strand breaks. However, the process of recombinational repair between short DNA regions of accidental similarity can lead to fatal genomic rearrangements. Previous studies have probed how effectively RecA discriminates against interactions involving a short similar sequence that is embedded in otherwise dissimilar sequences but have not yielded fully conclusive results. Here, we present results of in vitro experiments with fluorescent probes strategically located on the interacting DNA fragments used for recombination. Our findings suggest that DNA synthesis increases the stability of the recombination products. Fluorescence measurements can also probe the homology dependence of the extension of invading DNA strands in D-loops formed by RecA-mediated strand exchange. We examined the slow extension of the invading strand in a D-loop by DNA polymerase (Pol) IV and the more rapid extension by DNA polymerase LF-Bsu We found that when DNA Pol IV extends the invading strand in a D-loop formed by RecA-mediated strand exchange, the extension afforded by 82 bp of homology is significantly longer than the extension on 50 bp of homology. In contrast, the extension of the invading strand in D-loops by DNA LF-Bsu Pol is similar for intermediates with \≥50 bp of homology. These results suggest that fatal genomic rearrangements due to the recombination of small regions of accidental homology may be reduced if RecA-mediated strand exchange is immediately followed by DNA synthesis by a slow polymerase.

}, keywords = {cooperativity, DNA damage, DNA polymerase, DNA recombination, double-strand break (DSB), fluorescence resonance energy transfer (FRET), heteroduplex formation, molecular dynamics, RecA, strand displacement synthesis}, doi = {10.1074/jbc.RA119.007554}, author = {Lu, Daniel and Danilowicz, Claudia and Tashjian, Tommy F and Chantal Pr{\'e}vost and Godoy, Veronica G and Prentiss, Mara} } @article {2019|2065, title = {Weaving DNA strands: structural insight on ATP hydrolysis in RecA-induced homologous recombination}, journal = {Nucleic Acids Res}, volume = {47}, year = {2019}, month = {Sep}, pages = {7798-7808}, abstract = {

Homologous recombination is a fundamental process in all living organisms that allows the faithful repair of DNA double strand breaks, through the exchange of DNA strands between homologous regions of the genome. Results of three decades of investigation and recent fruitful observations have unveiled key elements of the reaction mechanism, which proceeds along nucleofilaments of recombinase proteins of the RecA family. Yet, one essential aspect of homologous recombination has largely been overlooked when deciphering the mechanism: while ATP is hydrolyzed in large quantity during the process, how exactly hydrolysis influences the DNA strand exchange reaction at the structural level remains to be elucidated. In this study, we build on a previous geometrical approach that studied the RecA filament variability without bound DNA to examine the putative implication of ATP hydrolysis on the structure, position, and interactions of up to three DNA strands within the RecA nucleofilament. Simulation results on modeled intermediates in the ATP cycle bring important clues about how local distortions in the DNA strand geometries resulting from ATP hydrolysis can aid sequence recognition by promoting local melting of already formed DNA heteroduplex and transient reverse strand exchange in a weaving type of mechanism.

}, doi = {10.1093/nar/gkz667}, author = {Boyer, Benjamin and Danilowicz, Claudia and Prentiss, Mara and Chantal Pr{\'e}vost} } @article {2018, title = {RecA requires two molecules of Mg2+ ions for its optimal strand exchange activity in vitro}, journal = {Nucleic Acids Res}, volume = {ahead of print}, year = {2018}, month = {Jan}, abstract = {

Mg2+ ion stimulates the DNA strand exchange reaction catalyzed by RecA, a key step in homologous recombination. To elucidate the molecular mechanisms underlying the role of Mg2+ and the strand exchange reaction itself, we investigated the interaction of RecA with Mg2+ and sought to determine which step of the reaction is affected. Thermal stability, intrinsic fluorescence, and native mass spectrometric analyses of RecA revealed that RecA binds at least two Mg2+ ions with KD \‚{\^a}{\`a} 2 mM and 5 mM. Deletion of the C-terminal acidic tail of RecA made its thermal stability and fluorescence characteristics insensitive to Mg2+ and similar to those of full-length RecA in the presence of saturating Mg2+. These observations, together with the results of a molecular dynamics simulation, support the idea that the acidic tail hampers the strand exchange reaction by interacting with other parts of RecA, and that binding of Mg2+ to the tail prevents these interactions and releases RecA from inhibition. We observed that binding of the first Mg2+ stimulated joint molecule formation, whereas binding of the second stimulated progression of the reaction. Thus, RecA is actively involved in the strand exchange step as well as bringing the two DNAs close to each other.

}, doi = {10.1093/nar/gky048}, author = {Kim, Raeyeong and Kanamaru, Shuji and Mikawa, Tsutomu and Chantal Pr{\'e}vost and Ishii, Kentaro and Ito, Kentaro and Uchiyama, Susumu and Oda, Masayuki and Iwasaki, Hiroshi and Kim, Seog K and Takahashi, Masayuki} } @article {2017|2022, title = {ATP hydrolysis provides functions that promote rejection of pairings between different copies of long repeated sequences}, journal = {Nucleic Acids Res}, volume = {45}, year = {2017}, pages = {8448-8462}, abstract = {

During DNA recombination and repair, RecA family proteins must promote rapid joining of homologous DNA. Repeated sequences with \>100 base pair lengths occupy more than 1\% of bacterial genomes; however, commitment to strand exchange was believed to occur after testing ~20-30 bp. If that were true, pairings between different copies of long repeated sequences would usually become irreversible. Our experiments reveal that in the presence of ATP hydrolysis even 75 bp sequence-matched strand exchange products remain quite reversible. Experiments also indicate that when ATP hydrolysis is present, flanking heterologous dsDNA regions increase the reversibility of sequence matched strand exchange products with lengths up to ~75 bp. Results of molecular dynamics simulations provide insight into how ATP hydrolysis destabilizes strand exchange products. These results inspired a model that shows how pairings between long repeated sequences could be efficiently rejected even though most homologous pairings form irreversible products.

}, doi = {10.1093/nar/gkx582}, author = {Danilowicz, Claudia and Hermans, Laura and Coljee, Vincent and Chantal Pr{\'e}vost and Prentiss, Mara} } @article {2017, title = {Mobility and core-protein binding patterns of disordered C-terminal tails in β-tubulin isotypes.}, journal = {Biochemistry}, volume = { 56}, year = {2017}, pages = {1746{\textendash}1756}, chapter = {1746}, abstract = {

Although they play a significant part in the regulation of microtubule structure, dynamics and function, the disordered C-terminal tails of tubulin remain invisible to experimental structural methods and do not appear in the crystallographic structures that are currently available in the Protein Data Bank. Interestingly, these tails concentrate most of the sequence variability between tubulin isotypes, and are the sites of the principal post-translational modifications undergone by this protein. Using homology modeling, we developed two complete models for the human αI/βI and αI/βIII tubulin isotypes that include their C-terminal tails. We then investigated the conformational variability of the two β-tails using long time-scale classical Molecular Dynamics (MD) simulations that revealed similar features, notably the unexpected presence of common anchoring regions on the surface of the tubulin dimer, but also distinctive mobility or interaction patterns, some of which could be related to the tail lengths and charge distributions. We also observed in our simulations that the C-terminal tail from the βI isotype, but not the βIII, formed contacts in the putative binding site of a recently discovered peptide that disrupts microtubule formation in glioma cells. Hindering the binding site in the βI isotype would be consistent with this peptide\’s preferential disruption of microtubule formation in glioma, whose cells overexpress βIII, compared to normal glial cells. While these observations need to be confirmed with more intensive sampling, our study opens up new perspectives for the development of isotype-specific chemotherapy drugs.

}, doi = {10.1021/acs.biochem.6b00988}, author = {Laurin, Yoann and Eyer, Joel and Charles H. Robert and Chantal Pr{\'e}vost and S Sacquin-Mora} } @article {2016|1763, title = {Structure of ring-shaped Aβ42 oligomers determined by conformational selection}, journal = {Sci. Rep.}, volume = {6}, year = {2016}, pages = {21429}, abstract = {

The oligomerization of amyloid beta (Aβ) peptides into soluble non-fibrillar species plays a critical role in the pathogenesis of Alzheimer\&$\#$39;s disease. However, it has been challenging to characterize the tertiary and quaternary structures of Aβ peptides due to their disordered nature and high aggregation propensity. In this work, replica exchange molecular dynamics simulations were used to explore the conformational space of Aβ42 monomer. Among the most populated transient states, we identified a particular conformation which was able to generate ring-shaped pentamers and hexamers, when docked onto itself. The structures of these aggregates were stable during microsecond all-atom MD simulations in explicit solvent. In addition to high resolution models of these oligomers, this study provides support for the conformational selection mechanism of Aβ peptide self-assembly.

}, issn = {2045-2322}, doi = {10.1038/srep21429}, author = {Tran, Linh and Basdevant, Nathalie and Chantal Pr{\'e}vost and Ha-Duong, T{\^a}p} } @article {2015|1766, title = {Docking Peptides on Proteins: How to Open a Lock, in the Dark, with a Flexible Key}, journal = {Structure}, volume = {23}, number = {8}, year = {2015}, month = {aug}, pages = {1373{\textendash}1374}, doi = {10.1016/j.str.2015.07.004}, author = {S Sacquin-Mora and Chantal Pr{\'e}vost} } @article {2015|1731, title = {Integrating multi-scale data on homologous recombination into a new recognition mechanism based on simulations of the RecA-ssDNA/dsDNA structure}, journal = {Nucleic Acids Res.}, volume = {43}, year = {2015}, month = {dec}, pages = {10251{\textendash}63}, abstract = {

RecA protein is the prototypical recombinase. Members of the recombinase family can accurately repair double strand breaks in DNA. They also provide crucial links between pairs of sister chromatids in eukaryotic meiosis. A very broad outline of how these proteins align homologous sequences and promote DNA strand exchange has long been known, as are the crystal structures of the RecA-DNA pre- and postsynaptic complexes; however, little is known about the homology searching conformations and the details of how DNA in bacterial genomes is rapidly searched until homologous alignment is achieved. By integrating a physical model of recognition to new modeling work based on docking exploration and molecular dynamics simulation, we present a detailed structure/function model of homology recognition that reconciles extremely quick searching with the efficient and stringent formation of stable strand exchange products and which is consistent with a vast body of previously unexplained experimental results.

}, doi = {10.1093/nar/gkv883}, author = {Yang, Darren and Boyer, Benjamin and Chantal Pr{\'e}vost and Danilowicz, Claudia and Prentiss, Mara} } @article {2015|1965, title = {An integrative approach to the study of filamentous oligomeric assemblies, with application to {R}ec{A}}, journal = {Plos One}, volume = {in press}, year = {2015}, pages = {e0116414}, abstract = {

Oligomeric macromolecules in the cell self-organize into a wide variety of geometrical motifs such as helices, rings or linear filaments. The recombinase proteins involved in homologous recombination present many such assembly motifs. Here, we examine in particular the polymorphic characteristics of RecA, the most studied member of the recombinase family, using an integrative approach that relates local modes of monomer/monomer association to the global architecture of their screw-type organization. In our approach, local modes of association are sampled via docking or Monte Carlo simulations. This enables shedding new light on fiber morphologies that may be adopted by the RecA protein. Two distinct RecA helical morphologies, the so-called \"extended\" and \"compressed\" forms, are known to play a role in homologous recombination. We investigate the variability within each form in terms of helical parameters and steric accessibility. We also address possible helical discontinuities in RecA filaments due to multiple monomer-monomer association modes. By relating local interface organization to global filament morphology, the strategies developed here to study RecA self-assembly are particularly well suited to other DNA-binding proteins and to filamentous protein assemblies in general.

}, doi = {10.1371/journal.pone.0116414}, author = {Benjamin Boyer and Johann Ezelin and Pierre Poulain and A Saladin and Martin Zacharias and Charles H. Robert and Chantal Pr{\'e}vost} } @article {2015|1586, title = {Investigating the Structural Variability and Binding Modes of the Glioma Targeting NFL-TBS.40-63 Peptide on Tubulin}, journal = {Biochemistry}, volume = {54}, number = {23}, year = {2015}, month = {jun}, pages = {3660{\textendash}3669}, doi = {10.1021/acs.biochem5b00146}, author = {Laurin, Y. and Savarin, P. and Charles H. Robert and M. Takahashi and Eyer, J. and Chantal Pr{\'e}vost and S Sacquin-Mora} } @article {2015|1732, title = {The poor homology stringency in the heteroduplex allows strand exchange to incorporate desirable mismatches without sacrificing recognition in vivo}, journal = {Nucleic Acids Res.}, volume = {43}, year = {2015}, month = {jul}, pages = {6473{\textendash}85}, abstract = {

RecA family proteins are responsible for homology search and strand exchange. In bacteria, homology search begins after RecA binds an initiating single-stranded DNA (ssDNA) in the primary DNA-binding site, forming the presynaptic filament. Once the filament is formed, it interrogates double-stranded DNA (dsDNA). During the interrogation, bases in the dsDNA attempt to form Watson-Crick bonds with the corresponding bases in the initiating strand. Mismatch dependent instability in the base pairing in the heteroduplex strand exchange product could provide stringent recognition; however, we present experimental and theoretical results suggesting that the heteroduplex stability is insensitive to mismatches. We also present data suggesting that an initial homology test of 8 contiguous bases rejects most interactions containing more than 1/8 mismatches without forming a detectable 20 bp product. We propose that, in vivo, the sparsity of accidental sequence matches allows an initial 8 bp test to rapidly reject almost all non-homologous sequences. We speculate that once the initial test is passed, the mismatch insensitive binding in the heteroduplex allows short mismatched regions to be incorporated in otherwise homologous strand exchange products even though sequences with less homology are eventually rejected.

}, doi = {10.1093/nar/gkv610}, author = {Danilowicz, Claudia and Yang, Darren and Kelley, Craig and Chantal Pr{\'e}vost and Prentiss, Mara} } @article {2015|1641, title = {Structure/function relationships in RecA protein-mediated homology recognition and strand exchange}, journal = {Crit. Rev. Biochem. Mol. Biol.}, volume = {50}, year = {2015}, pages = {453{\textendash}76}, abstract = {RecA family proteins include RecA, Rad51, and Dmc1. These recombinases are responsible for homology search and strand exchange. Homology search and strand exchange occur during double-strand break repair and in eukaryotes during meiotic recombination. In bacteria, homology search begins when RecA binds an initiating single-stranded DNA (ssDNA) in the primary DNA-binding site to form the presynaptic filament. The filament is a right-handed helix, where the initiating strand is bound deep within the filament. Once the presynaptic filament is formed, it interrogates nearby double-stranded DNA (dsDNA) to find a homologous sequence; therefore, we provide a detailed discussion of structural features of the presynaptic filament that play important functional roles. The discussion includes many diagrams showing multiple filament turns. These diagrams illustrate interactions that are not evident in single turn structures. The first dsDNA interactions with the presynaptic filament are insensitive to mismatches. The mismatch insensitive interactions lead to dsDNA deformation that triggers a homology testing process governed by kinetics. The first homology test involves {\^a}ˆ{\textonequarter}8 bases. Almost all interactions are rejected by this initial rapid test, leading to a new cycle of homology testing. Interactions that pass the initial rapid test proceed to a slower testing stage. That slower stage induces nonhomologous dsDNA to reverse strand exchange and begin a new cycle of homology testing. In contrast, homologous dsDNA continues to extend the heteroduplex strand-exchange product until ATP hydrolysis makes strand exchange irreversible.}, keywords = {Double-strand break repair, meiosis, meiotic recombination, Rad51, recombinase}, doi = {10.3109/10409238.2015.1092943}, author = {Prentiss, Mara and Chantal Pr{\'e}vost and Danilowicz, Claudia} } @article {2012|1934, title = {{ATTRACT} and {PTOOLS}: {O}pen source programs for protein-protein docking}, journal = {Methods Mol. Biol.}, volume = {819}, year = {2012}, pages = {221{\textendash}232}, abstract = {

The prediction of the structure of protein-protein complexes based on structures or structural models of isolated partners is of increasing importance for structural biology and bioinformatics. The ATTRACT program can be used to perform systematic docking searches based on docking energy minimization. It is part of the object-oriented PTools library written in Python and C++. The library contains various routines to manipulate protein structures, to prepare and perform docking searches as well as analyzing docking results. It also intended to facilitate further methodological developments in the area of macromolecular docking that can be easily integrated. Here, we describe the application of PTools to perform systematic docking searches and to analyze the results. In addition, the possibility to perform multi-component docking will also be presented.

}, doi = {10.1007/978-1-61779-465-0_15}, author = {Schneider, S. and A Saladin and Fiorucci, S. and Chantal Pr{\'e}vost and Martin Zacharias} } @article {2012|1527, title = {{S}tructure-function analysis of the {NFL}-{TBS}.40-63 peptide corresponding to the binding site of tubulin on the light neurofilament subunit}, journal = {Plos One}, volume = {7}, year = {2012}, pages = {e49436}, author = {Berges, R. and Balzeau, J. and Takahashi, M. and Chantal Pr{\'e}vost and Eyer, J.} } @article {2011|1654, title = {Accounting for large amplitude protein deformation during in silico macromolecular docking}, journal = {Int. J. Mol. Sci.}, volume = {12}, year = {2011}, pages = {1316{\textendash}33}, abstract = {

Rapid progress of theoretical methods and computer calculation resources has turned in silico methods into a conceivable tool to predict the 3D structure of macromolecular assemblages, starting from the structure of their separate elements. Still, some classes of complexes represent a real challenge for macromolecular docking methods. In these complexes, protein parts like loops or domains undergo large amplitude deformations upon association, thus remodeling the surface accessible to the partner protein or DNA. We discuss the problems linked with managing such rearrangements in docking methods and we review strategies that are presently being explored, as well as their limitations and success.

}, keywords = {flexibility, macromolecular docking, protein loops and domains}, doi = {10.3390/ijms12021316}, author = {Bastard, Karine and A Saladin and Chantal Pr{\'e}vost} } @article {2011|1653, title = {On the characterization and selection of diverse conformational ensembles with applications to flexible docking}, journal = {Ieee/acm Trans. Comput. Biol. Bioinform.}, volume = {8}, year = {2011}, pages = {487{\textendash}98}, abstract = {

To address challenging flexible docking problems, a number of docking algorithms pregenerate large collections of candidate conformers. To remove the redundancy from such ensembles, a central problem in this context is to report a selection of conformers maximizing some geometric diversity criterion. We make three contributions to this problem. First, we resort to geometric optimization so as to report selections maximizing the molecular volume or molecular surface area (MSA) of the selection. Greedy strategies are developed, together with approximation bounds. Second, to assess the efficacy of our algorithms, we investigate two conformer ensembles corresponding to a flexible loop of four protein complexes. By focusing on the MSA of the selection, we show that our strategy matches the MSA of standard selection methods, but resorting to a number of conformers between one and two orders of magnitude smaller. This observation is qualitatively explained using the Betti numbers of the union of balls of the selection. Finally, we replace the conformer selection problem in the context of multiple-copy flexible docking. On the aforementioned systems, we show that using the loops selected by our strategy can improve the result of the docking process.

}, doi = {10.1109/TCBB.2009.59}, author = {Loriot, S{\'e}bastien and Sachdeva, Sushant and Bastard, Karine and Chantal Pr{\'e}vost and Fr{\'e}d{\'e}ric Cazals} } @article {2011|1748, title = {Optimizing the design of oligonucleotides for homology directed gene targeting}, journal = {Plos One}, volume = {6}, year = {2011}, pages = {e14795}, abstract = {

BACKGROUND: Gene targeting depends on the ability of cells to use homologous recombination to integrate exogenous DNA into their own genome. A robust mechanistic model of homologous recombination is necessary to fully exploit gene targeting for therapeutic benefit. METHODOLOGY/PRINCIPAL FINDINGS: In this work, our recently developed numerical simulation model for homology search is employed to develop rules for the design of oligonucleotides used in gene targeting. A Metropolis Monte-Carlo algorithm is used to predict the pairing dynamics of an oligonucleotide with the target double-stranded DNA. The model calculates the base-alignment between a long, target double-stranded DNA and a probe nucleoprotein filament comprised of homologous recombination proteins (Rad51 or RecA) polymerized on a single strand DNA. In this study, we considered different sizes of oligonucleotides containing 1 or 3 base heterologies with the target; different positions on the probe were tested to investigate the effect of the mismatch position on the pairing dynamics and stability. We show that the optimal design is a compromise between the mean time to reach a perfect alignment between the two molecules and the stability of the complex. CONCLUSION AND SIGNIFICANCE: A single heterology can be placed anywhere without significantly affecting the stability of the triplex. In the case of three consecutive heterologies, our modeling recommends using long oligonucleotides (at least 35 bases) in which the heterologous sequences are positioned at an intermediate position. Oligonucleotides should not contain more than 10\% consecutive heterologies to guarantee a stable pairing with the target dsDNA. Theoretical modeling cannot replace experiments, but we believe that our model can considerably accelerate optimization of oligonucleotides for gene therapy by predicting their pairing dynamics with the target dsDNA.

}, doi = {10.1371/journal.pone.0014795}, author = {Min{\'e}-Hattab, Judith and Fleury, Genevi{\`e}ve and Chantal Pr{\'e}vost and Dutreix, Marie and Viovy, Jean-Louis} } @article {2010|1512, title = {{M}odeling the early stage of {D}{N}{A} sequence recognition within {R}ec{A} nucleoprotein filaments}, journal = {Nucleic Acids Res.}, volume = {38}, year = {2010}, month = {oct}, pages = {6313{\textendash}6323}, author = {A Saladin and Amourda, C. and Poulain, P. and Nicolas F{\'e}rey and Marc Baaden and Martin Zacharias and Delalande, O. and Chantal Pr{\'e}vost} } @inbook {2010|1758, title = {Protein-Protein Docking}, booktitle = {Protein-Protein Complexes. Analysis, Modeling and Drug Design}, year = {2010}, pages = {147{\textendash}181}, publisher = {Imperial College Press}, organization = {Imperial College Press}, chapter = {6}, author = {A Saladin and Chantal Pr{\'e}vost}, editor = {Martin Zacharias} } @article {2009|1636, title = {Deforming DNA: from physics to biology}, journal = {Chemphyschem}, volume = {10}, year = {2009}, month = {jul}, pages = {1399{\textendash}404}, abstract = {

The DNA double helix has become a modern icon which symbolizes our understanding of the molecular basis of life. It is less widely recognized that the double helix proposed by Watson and Crick more than half a century ago is a remarkably adaptable molecule that can undergo major conformational rearrangements without being irreversibly damaged. Indeed, DNA deformation is an intrinsic feature of many of the biological processes in which it is involved. Over the last two decades, single-molecule experiments coupled with molecular modeling have transformed our understanding of DNA flexibility, while the accumulation of high-resolution structures of DNA-protein complexes have demonstrated how organisms can exploit this property as a useful feature for preserving, reading, replicating, and packaging the genetic message. In this Minireview we summarize the information now available on the extreme\–and the less extreme\–deformations of the double helix.

}, doi = {10.1002/cphc.200900253}, author = {Chantal Pr{\'e}vost and M. Takahashi and Richard Lavery} } @article {2009|1392, title = {{PT}ools: an opensource molecular docking library.}, journal = {Bmc Struct. Biol.}, volume = {9}, year = {2009}, pages = {27{\textendash}37}, doi = {10.1186/1472-6807-9-27}, author = {A Saladin and Fiorucci, S and Poulain, P and Chantal Pr{\'e}vost and Martin Zacharias} } @article {2008|1662, title = {Insights on protein-DNA recognition by coarse grain modelling}, journal = {J. Comput. Chem.}, volume = {29}, year = {2008}, month = {nov}, pages = {2582{\textendash}92}, abstract = {

Coarse grain modelling of macromolecules is a new approach, potentially well adapted to answer numerous issues, ranging from physics to biology. We propose here an original DNA coarse grain model specifically dedicated to protein-DNA docking, a crucial, but still largely unresolved, question in molecular biology. Using a representative set of protein-DNA complexes, we first show that our model is able to predict the interaction surface between the macromolecular partners taken in their bound form. In a second part, the impact of the DNA sequence and electrostatics, together with the DNA and protein conformations on docking is investigated. Our results strongly suggest that the overall DNA structure mainly contributes in discriminating the interaction site on cognate proteins. Direct electrostatic interactions between phosphate groups and amino acid side chains strengthen the binding. Overall, this work demonstrates that coarse grain modeling can reveal itself a precious auxiliary for a general and complete description and understanding of protein-DNA association mechanisms.

}, doi = {10.1002/jcc.21014}, author = {Poulain, P and A Saladin and Hartmann, B and Chantal Pr{\'e}vost} } @inbook {2008|1565, title = {Recombination and Meiosis : Models, Means and Evolution Coll. Genome Dynamics \& Stability}, booktitle = {Genome Dynamics \& Stability}, volume = {3}, year = {2008}, pages = {65{\textendash}84}, publisher = {Springer Verlag Berlin Heidleberg}, organization = {Springer Verlag Berlin Heidleberg}, chapter = {Searching for Homology by Filaments of RecA-like Proteins}, author = {Chantal Pr{\'e}vost}, editor = {Richard Egel and Dirk-Henner Lankenau} } @inbook {2008|1651, title = {Searching for Homology by Filaments of RecA-like Proteins}, booktitle = {Genome Dynamics \& Stability}, volume = {Recombination and Meiosis. Models, Means and Evolution}, number = {3}, year = {2008}, pages = {65{\textendash}89}, publisher = {Springer Verlag}, organization = {Springer Verlag}, edition = {Richard Egel and Dirk-Henner Lankenau}, address = {Berlin Heidelberg}, abstract = {

The recombinase proteins of the RecA family perform tasks that are essential for cell survival and for the maintenance of genetic diversity. They are able to rearrange genes in new combinations and to repair DNA double-strand breaks in an almost error-free fashion. Their function in homologous recombination is performed in an original way that has no equivalent in the DNA processing machinery: They form long helical filaments on a target DNA, capable of recognizing homologous DNA sequences in the genome and of exchanging DNA strands. How the DNA sequences are recognized during this process and how the DNA strands are exchanged remain matters of investigation. This chapter reviews the information that has been accumulated on recognition and strand exchange, together with the models that aim at organizing this data, viewed at different levels: that of the nucleus, the molecule, or the atom. Altogether, a picture begins to emerge on a multiscale dimension, which presents the search for homology as a complex process with important dynamic components.

}, author = {Chantal Pr{\'e}vost}, editor = {Richard Egel and Dirk Henner-Lankenau} } @inbook {2007|1774, title = {{F}lexible macromolecular docking: {A}n overview of recent progress}, volume = {Recent Research Adv. in Structural BioInformatics}, year = {2007}, pages = {249{\textendash}274}, publisher = {Research Signpost}, organization = {Research Signpost}, chapter = {10}, author = {K. Bastard and Chantal Pr{\'e}vost}, editor = {A. G. De Brevern} } @inbook {2007|1563, title = {Recent Research Adv. in Structural BioInformatics}, year = {2007}, pages = {249{\textendash}274}, publisher = {Research signpost, Trivandrum, India}, organization = {Research signpost, Trivandrum, India}, chapter = {Flexible macromolecular docking: An overview of recent progress}, author = {K. Bastard and Chantal Pr{\'e}vost}, editor = {A.G. de Brevern} } @article {2006|1536, title = {Accounting for loop flexibility during protein-protein docking}, journal = {Proteins}, volume = {62}, number = {4}, year = {2006}, month = {mar}, pages = {956{\textendash}969}, author = {Bastard, K and Chantal Pr{\'e}vost and Martin Zacharias} } @article {2004|1825, title = {Identification of the subunit-subunit interface of Xenopus Rad51.1 protein: Similarity to RecA}, journal = {J. Mol. Biol.}, volume = {335}, number = {4}, year = {2004}, month = {jan}, pages = {895{\textendash}904}, abstract = {

Rad51, like its prokaryotic homolog RecA, forms a helical filament for homologous DNA recombination and recombinational DNA repair. Comparison of the three-dimensional structures of human Rad51 and Escherichia coli RecA indicated that the tyrosine residue at position 191 in human Rad51 lies at the centre of a putative subunit-subunit contact interface. We inserted a tryptophan residue as a fluorescent probe at the corresponding position in Xenopus Rad51.1 and found that its fluorescence depended upon the protein concentration, indicating that the residue is truly in the subunit-subunit interface. We also found that 3 M urea, which promoted the dissociation of Rad51 filament without complete unfolding of the protein, exposed the tryptophan residue to solvent. The fluorescence was not modified by binding to DNA and only slightly modified by ATP, indicating that the same site is used for formation of the active ATP-Rad51-DNA filament. The slight changes in fluorescence caused by ATP and ADP suggest that the subunit-subunit contact is altered, leading to the elongation of the filament by these nucleotides, as with the RecA filament. Thus, Rad51 forms filaments by subunit-subunit contact much like RecA does.

}, author = {Selmane, T and Camadro, JM and Conilleau, S and Fleury, F and Tran, V and Chantal Pr{\'e}vost and Takahashi, M} } @article {2003|1663, title = {Docking macromolecules with flexible segments}, journal = {J. Comput. Chem.}, volume = {24}, year = {2003}, month = {nov}, pages = {1910{\textendash}20}, abstract = {

We address a major obstacle to macromolecular docking algorithms by presenting a new method that takes into account the induced conformational adjustment of flexible loops situated at a protein/macromolecule interface. The method, MC2, is based on a multiple copy representation of the loops, coupled with a Monte Carlo conformational search of the relative position of the macromolecules and their side chain conformations. The selection of optimal loop conformations takes place during Monte Carlo cycling by the iterative adjustment of the weight of each copy. We describe here the parameterization of the method and trials on a protein-DNA complex of known 3-D structure, involving the Drosophila prd paired domain protein and its target oligonucleotide Wenqing, X. et al., Cell 1995, 80, 639. We demonstrate that our algorithm can correctly configure and position this protein, despite its relatively complex interactions with both grooves of DNA.

}, doi = {10.1002/jcc.10329}, author = {Bastard, Karine and Thureau, Aur{\'e}lien and Richard Lavery and Chantal Pr{\'e}vost} } @article {2003|1761, title = {Geometry of the DNA strands within the RecA nucleofilament: role in homologous recombination}, journal = {Q. Rev. Biophys.}, volume = {36}, year = {2003}, month = {nov}, pages = {429{\textendash}53}, abstract = {

Homologous recombination consists of exchanging DNA strands of identical or almost identical sequence. This process is important for both DNA repair and DNA segregation. In prokaryotes, it involves the formation of long helical filaments of the RecA protein on DNA. These filaments incorporate double-stranded DNA from the cell\&$\#$39;s genetic material, recognize sequence homology and promote strand exchange between the two DNA segments. DNA processing by these nucleofilaments is characterized by large amplitude deformations of the double helix, which is stretched by 50\% and unwound by 40\% with respect to B-DNA. In this article, information concerning the structure and interactions of the RecA, DNA and ATP molecules involved in DNA strand exchange is gathered and analyzed to present a view of their possible arrangement within the filament, their behavior during strand exchange and during ATP hydrolysis, the mechanism of RecA-promoted DNA deformation and the role of DNA deformation in the process of homologous recombination. In particular, the unusual characteristics of DNA within the RecA filament are compared to the DNA deformations locally induced by architectural proteins which bind in the DNA minor groove. The possible role and location of two flexible loops of RecA are discussed.

}, author = {Chantal Pr{\'e}vost and M. Takahashi} } @article {2000|1431, title = {A mechanism for RecA-promoted sequence homology recognition and strand exchange between single-stranded DNA and duplex DNA, via triple-helical intermediates}, journal = {J. Biomol. Struct. Dyn.}, number = {Sp. Iss. S1}, year = {2000}, note = {11th Conversation in Biomolecular Stereodynamics, ALBANY, NEW YORK, JUN 15-19, 1999}, pages = {147{\textendash}153}, author = {Bertucat, G and Lavery, R and Chantal Pr{\'e}vost} } @article {1999|1600, title = {A molecular model for RecA-promoted strand exchange via parallel triple-stranded helices}, journal = {Biophys. J.}, volume = {77}, year = {1999}, month = {sep}, pages = {1562{\textendash}76}, abstract = {

A number of studies have concluded that strand exchange between a RecA-complexed DNA single strand and a homologous DNA duplex occurs via a single-strand invasion of the minor groove of the duplex. Using molecular modeling, we have previously demonstrated the possibility of forming a parallel triple helix in which the single strand interacts with the intact duplex in the minor groove, via novel base interactions (Bertucat et al., J. Biomol. Struct. Dynam. 16:535-546). This triplex is stabilized by the stretching and unwinding imposed by RecA. In the present study, we show that the bases within this triplex are appropriately placed to undergo strand exchange. Strand exchange is found to be exothermic and to result in a triple helix in which the new single strand occupies the major groove. This structure, which can be equated to so-called R-form DNA, can be further stabilized by compression and rewinding. We are consequently able to propose a detailed, atomic-scale model of RecA-promoted strand exchange. This model, which is supported by a variety of experimental data, suggests that the role of RecA is principally to prepare the single strand for its future interactions, to guide a minor groove attack on duplex DNA, and to stabilize the resulting, stretched triplex, which intrinsically favors strand exchange. We also discuss how this mechanism can incorporate homologous recognition.

}, doi = {10.1016/S0006-3495(99)77004-9}, author = {Bertucat, G and Richard Lavery and Chantal Pr{\'e}vost} } @article {1998|1659, title = {A model for parallel triple helix formation by RecA: single-single association with a homologous duplex via the minor groove}, journal = {J. Biomol. Struct. Dyn.}, volume = {16}, year = {1998}, month = {dec}, pages = {535{\textendash}46}, abstract = {

The nucleoproteic filaments of RecA polymerized on single stranded DNA are able to integrate double stranded DNA in a coaxial arrangement (with DNA stretched by a factor 1.5), to recognize homologous sequences in the duplex and to perform strand exchange between the single stranded and double stranded molecules. While experimental results favor the hypothesis of an invasion of the minor groove of the duplex by the single strand, parallel minor groove triple helices have never been isolated or even modeled, the minor groove offering little space for a third strand to interact. Based on an internal coordinate modeling study, we show here that such a structure is perfectly conceivable when the two interacting oligomers are stretched by a factor 1.5, in order to open the minor groove of the duplex. The model helix presents characteristics that coincide with known experimental data on unwinding, base pair inclination and inter-proton distances. Moreover, we show that extension and unwinding stabilize the triple helix. New patterns of triplet interaction via the minor groove are presented.

}, doi = {10.1080/07391102.1998.10508268}, author = {Bertucat, G and Richard Lavery and Chantal Pr{\'e}vost} } @article {1997|1680, title = {Collective-variable Monte Carlo simulation of DNA}, journal = {J. Comp. Chem.}, volume = {18}, year = {1997}, pages = {2001{\textendash}2011}, author = {H. Gabb and Chantal Pr{\'e}vost and G. Bertucat and Charles H. Robert and Richard Lavery} } @article {1997|1819, title = {Distortions of the DNA double helix induced by 1,3-trans-diamminedichloroplatinum(II)-intrastrand cross-link: An internal coordinate molecular modeling study}, journal = {J. Biomol. Struct. Dyn.}, volume = {14}, number = {6}, year = {1997}, month = {jun}, pages = {703{\textendash}714}, abstract = {

A trans-diamminedichloroplatinum(II) (trans-DDP) intrastrand adduct within the sequence d(TCTG*TG*TC).d(GACACAGA) (where G* represents a platinated guanine) is modeled on the basis of qualitative experimental data concerning global unwinding and curvature as well as information on base pairing. Modeling is performed using the internal coordinate JUMNA program, specific to nucleic acids, and modified to include the possibility of covalently bound ligands. Calibration of the energy functions representing the Pt-N7 bond with guanine is described. The platinum atom and the platinum-nitrogen bonds are parameterized for use in the H{\"u}ckel Del Re method to calculate monopoles at each atom. These monopoles are consistent with the Flex force field included in Jumna. By developing an appropriate minimization protocol we are able to generate stable, distorted three-dimensional structures compatible with the experimental data and including an unusually high global unwinding. No a priori geometric assumptions are made in generating these structures.

}, doi = {10.1080/07391102.1997.10508173}, author = {Chantal Pr{\'e}vost and Boudvillain, M and Beudaert, P and Leng, M and Lavery, R and Vovelle, F} } @article {1996|1666, title = {Finding and visualizing nucleic acid base stacking}, journal = {J Mol Graph}, volume = {14}, number = {1}, year = {1996}, month = {feb}, pages = {6{\textendash}11}, author = {Gabb, H A and Sanghani, S R and Charles H. Robert and Chantal Pr{\'e}vost} } @article {1996|1660, title = {Molecular modelling study of the netropsin complexation with a nucleic acid triple helix}, journal = {J. Biomol. Struct. Dyn.}, volume = {14}, year = {1996}, month = {dec}, pages = {293{\textendash}302}, abstract = {

A detailed molecular mechanical study has been made on the complexes of netropsin with the double stranded oligonucleotide (dA)12.(dT)12 and with the triple helix (dA)12.(dT)12.(dT)12. The complexes were built using computer graphics and energy refined using JUMNA program. In agreement with circular dichroism experiments we have shown that 3 netropsins can bind the minor grooves of the triple helix and of the double helix. The groove geometry in the duplex and in the triplex is very similar. However a detailed analysis of the energetic terms shows, in agreement with thermal denaturation studies, that the affinity of netropsin toward the double helices is larger than towards triple helices.

}, doi = {10.1080/07391102.1996.10508125}, author = {Vovelle, F and Chantal Pr{\'e}vost and Durand, M and Maurizot, J C} } @article {1995|1681, title = {Efficient conformational space sampling for nucleosides using internal coordinate Monte-Carlo simulations and a modified furanose description}, journal = {J. Comput. Chem.}, volume = {16}, year = {1995}, month = {jun}, pages = {667{\textendash}680}, chapter = {667}, abstract = {

Internal coordinates can be very helpful in modeling large biomacromolecules because freezing stiffer degrees of freedom, such as bond lengths, strongly reduces the number of variables describing the system. This, however, leads to difficulties in treating flexible rings such as the furanose sugars of nucleic acids or the proline residues of proteins, for which internal coordinates are an overcomplete description. We present here a new, internal coordinate furanose model based on the pseudorotational variables phase and amplitude which avoids having to solve a ring closure problem. The choice of a two- rather than a four-variable description is justified by a detailed analysis of molecular dynamic simulations. The efficiency and accuracy of the method are also demonstrated using extensive Monte Carlo simulations. This method of ring treatment is fast and well adapted to macromolecular simulations. (C) 1995 by John Wiley \& Sons, Inc.

}, issn = {0192-8651}, author = {Gabb, HA and Richard Lavery and Chantal Pr{\'e}vost} } @article {1995, title = {Radiation-induced damages in single- and double-stranded DNA}, journal = {Int. J. Radiat. Biol.}, volume = {67}, year = {1995}, month = {feb}, pages = {169{\textendash}76}, abstract = {

In the present study, we searched for possible effects of DNA strandedness (single and double), on two types of damages, frank strand breaks (FSB, observed at neutral pH) and alkali labile sites (ALS, leading to breaks at alkaline pH) induced by irradiation with gamma-rays (60Co) or fast neutrons (p34,Be). Sequencing gel electrophoresis allowed us to follow the occurrence of these damages at each nucleotide site in single (ss-ss), double (ds-ds), and half single-half double (ss-ds and ds-ss) stranded oligonucleotides. Globally, in DNA with random sequences of bases, no differences in FSB and ALS yield between the single and the double-stranded conformations were observed. One observes, however, an increased alkaline lability at some guanine sites belonging to single-stranded region of ss-ds or ds-ss. Nevertheless, strandedness influences the radiosensitivity of some particular sequences, i.e. the 5\&$\#$39;-AATT sequences. This region is less radiosensitive than the rest of DNA in the double helical, but not in the single-stranded conformation. The results are discussed in terms of DNA conformation.

}, author = {Isabelle, V and Chantal Pr{\'e}vost and Spotheim-Maurizot, M and Sabattier, R and Charlier, M} } @article {1995|1941, title = {Solution structure of oligonucleotides covalently linked to a psoralen derivative.}, journal = {Nucleic Acids Res.}, volume = {23}, number = {5}, year = {1995}, month = {mar}, pages = {788{\textendash}795}, abstract = {

Psoralen (pso) was attached via its C-5 position to the 5\&$\#$39;-phosphate group of an oligodeoxynucleotide d(TAAGCCG) by a hexamethylene linker (m6). Complex formation between pso-m6-d(TAAGCCG) and the complementary strands d(CGGCTTA)[7-7mer] or d(CGGCTTAT)[7-8mer] was investigated by nuclear magnetic resonance in aqueous solution. Structural informations derived from DQF-COSY and NOESY maps, revealed that the mini double helix adopts a B-form conformation and that the deoxyriboses preferentially adopt a C2\&$\#$39;-endo conformation. The nOe connectivities observed between the protons of the bases or the sugars in each duplex, and the protons of the psoralen and the hexamethylene chain, led us to propose a model involving an equilibrium between two conformations due to different locations of the psoralen. Upon UV-irradiation, the psoralen moiety cross-linked the two DNA strands at the level of 5\&$\#$39;TpA3\&$\#$39; sequences. NMR studies of the single major photo-cross-linked duplex pso-m6-d(TAAGCCG) and d(CGGCTTA) were performed. The stereochemistry of the diadduct is indeed cis-syn at both cyclobutane rings. In addition, the effects of this diadduct on the helical structure are analyzed in detail.

}, keywords = {Base Sequence, chemistry, chemistry/radiation effects, Magnetic Resonance Spectroscopy, Models, Molecular, Molecular Sequence Data, Nucleic Acid Conformation, Oligodeoxyribonucleotides, Psoralens, Solutions}, author = {O. Bornet and Chantal Pr{\'e}vost and F. Vovelle and M. Chassignol and N. T. Thuong and G. Lancelot} } @article {1993|1628, title = {Persistence analysis of the static and dynamical helix deformations of DNA oligonucleotides: application to the crystal structure and molecular dynamics simulation of d(CGCGAATTCGCG)2}, journal = {Biopolymers}, volume = {33}, year = {1993}, month = {mar}, pages = {335{\textendash}50}, abstract = {

A theory and graphical presentation for the analysis of helix structure and deformations in oligonucleotides is presented. The parameters \"persistence\" and \"flexibility\" as defined in the configurational statistics of polymers of infinite length are reformulated at the oligonucleotide level in an extension of J. A. Schellman\&$\#$39;s method [(1974) Biopolymers, Vol. 17, pp. 217-226], and used as a basis for a systematic \"Persistence Analysis\" of the helix deformation properties for all possible subsequences in the structure. The basis for the analysis is a set of link vectors referenced to individual base pairs, and is limited to sequences exhibiting only perturbed rod-like behavior, i.e., below the threshold for supercoiling. The present application of the method is concerned with a physical model for the angular component of bending, so the link vectors are defined as the unit components of a global helix axis obtained by the procedure \"Curves\" of R. Lavery and H. Sklenar [(1988) J. Biomol. Struct. Dynam., Vol. 6, pp. 63-91; (1989) ibid., Vol. 6, pp. 655-667]. A discussion of the relationship between global bending and relative orientation of base pairs is provided. Our approach is illustrated by analysis of some model oligonucleotide structures with intrinsic kinks, the crystal structure of the dodecamer d(CGCGAATTCGCG)2, and the results of two molecular dynamics simulations on this dodecamer using two variations of the GROMOS force field. The results indicate that essentially all aspects of curvature in short oligonucleotides can be determined, such as the position and orientation of each bend, the sharpness or smoothness, and the location and linearity of subsequences. In the case of molecular dynamics simulations, where a Boltzmann ensemble of structures is analyzed, the spatial extent of the deformations (flexibility) is also considered.

}, doi = {10.1002/bip.360330303}, author = {Chantal Pr{\'e}vost and Louise-May, S and Ravishanker, G and Richard Lavery and Beveridge, D L} } @article {1991|1767, title = {Mechanism of the rearrangement of the bicyclo [4.2. 0] octan system to the bicyclo [3.2. 1] octan system}, journal = {Tetrahedron}, volume = {47}, year = {1991}, pages = {229{\textendash}238}, abstract = {

A concerted mechanism has been demonstrated for the rearrangement of a tetracyclic ion including a bicyclo [4.2.0] octan system to hibaol, using a selective deuteration on the migrating bond. The stereochemistry of the selectively introduced deuterium was determined by three routes: 1. comparison of the high field 1H NMR spectra of the deuterated and undeuterated compounds, using double irradiation; 2. high field 1H NMR, coupled with molecular mechanics calculations; 3. two dimensional homo and heteronuclear NMR.

}, doi = {10.1016/S0040-4020(01)80919-4}, url = {http://www.sciencedirect.com/science/article/pii/S0040402001809194}, author = {Bastard, Josette and Do Khac, Duc and Fetizon, Marcel and Chantal Pr{\'e}vost and Beloeil, Jean-Claude} } @conference {1991|1580, title = {Methodological considerations on molecular dynamics simulations of DNA oligonucleotides}, booktitle = {AIP Conference Proceedings}, year = {1991}, month = {oct}, publisher = {AIP}, organization = {AIP}, abstract = {

Methodological aspects of solvent effects, simulation protocol, analysis and visualization of results, accuracy, and sensitivity of results to force field parametrization are discussed for molecular dynamics simulation on oligonucleotides. Recent results comparing AMBER, CHARMM and GROMOS force fields are included. The calculation of build\‚{\"A}{\^e}up curves for the nuclear Overhauser effect from simulations is also described.

}, doi = {10.1063/1.41314}, author = {Beveridge, DL and Swaminathan, S and Ravishanker, G and Withka, J and Srinivasan, J and Chantal Pr{\'e}vost and Louise-May, S and DiCapua, FM and Bolton, PH} } @article {1991|1719, title = {NMR and conformational studies of the cyclobutane ring involved in the bicyclo [4.2. 0] octane system of a tetracyclic diterpene structure}, journal = {Magn. Reson. Chem.}, volume = {29}, year = {1991}, pages = {870{\textendash}877}, abstract = {

Conformational studies were performed on the bicyclo [4.2.0] octane system of a series of related tetracyclic diterpenes, using molecular mechanics and 1H NMR. Both methods gave compatible results, but did not permit the deduction of any quantitative relationship linking the vicinal coupling constants to the cyclobutane dihedral angles. Nevertheless, the Karplus relationship allowed a qualitative interpretation of the coupling constants in terms of conformation. A set of characteristic 1H NMR coupling constants was obtained which allows the interpretation of the 1H NMR spectrum of any compound presenting a similar system.

}, doi = {DOI: 10.1002/mrc.1260290903}, url = {http://onlinelibrary.wiley.com/doi/10.1002/mrc.1260290903/full}, author = {Do Khac Manh, Duc and Fetizon, Marcel and Chantal Pr{\'e}vost and Roy, Pierre} } @inbook {1989|1579, title = {Stereospecific Ion-Molecule reactions in the collision cell induced by nucleophilic gas phase reagents on CI/NH4+ protonated diastereoisomeric tetracyclic terpenes.}, booktitle = {Advances in Mass Spectrometry}, volume = {11}, year = {1989}, pages = {1056}, edition = {P. Longevialle, Heyden and Son, Ed, New York}, author = {Cole, RB and Chantal Pr{\'e}vost and Tabet, JC} } @article {1986|1652, title = {Ion-Molecule reaction in the gas phase part VI Regioselective SN2 reaction from terpenoid diastereoisomeric diols using CI/NH 4+}, journal = {Helv. Chim. Acta}, volume = {69}, year = {1986}, pages = {806{\textendash}815}, abstract = {

A stereospecific and regioselective SN2 mechanism (Walden inversion) is observed during studies involving modified terpenoid epimeric diols in a high-pressure ion source using ammonia as a reagent gas.

}, doi = {10.1002/hlca.19860690408}, author = {Tabet, Jean-Claude and Chantal Pr{\'e}vost and Bouillot, Anne and Bastard, Josette and Manh, Due Do Khae and Tondeur, Yves} }