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  • 1
    Publication Date: 2011-10-25
    Description: Homologous recombination is a high-fidelity DNA repair pathway. Besides a critical role in accurate chromosome segregation during meiosis, recombination functions in DNA repair and in the recovery of stalled or broken replication forks to ensure genomic stability. In contrast, inappropriate recombination contributes to genomic instability, leading to loss of heterozygosity, chromosome rearrangements and cell death. The RecA/UvsX/RadA/Rad51 family of proteins catalyses the signature reactions of recombination, homology search and DNA strand invasion. Eukaryotes also possess Rad51 paralogues, whose exact role in recombination remains to be defined. Here we show that the Saccharomyces cerevisiae Rad51 paralogues, the Rad55-Rad57 heterodimer, counteract the antirecombination activity of the Srs2 helicase. The Rad55-Rad57 heterodimer associates with the Rad51-single-stranded DNA filament, rendering it more stable than a nucleoprotein filament containing Rad51 alone. The Rad51-Rad55-Rad57 co-filament resists disruption by the Srs2 antirecombinase by blocking Srs2 translocation, involving a direct protein interaction between Rad55-Rad57 and Srs2. Our results demonstrate an unexpected role of the Rad51 paralogues in stabilizing the Rad51 filament against a biologically important antagonist, the Srs2 antirecombination helicase. The biological significance of this mechanism is indicated by a complete suppression of the ionizing radiation sensitivity of rad55 or rad57 mutants by concomitant deletion of SRS2, as expected for biological antagonists. We propose that the Rad51 presynaptic filament is a meta-stable reversible intermediate, whose assembly and disassembly is governed by the balance between Rad55-Rad57 and Srs2, providing a key regulatory mechanism controlling the initiation of homologous recombination. These data provide a paradigm for the potential function of the human RAD51 paralogues, which are known to be involved in cancer predisposition and human disease.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3213327/" target="_blank"〉〈img src="https://static.pubmed.gov/portal/portal3rc.fcgi/4089621/img/3977009" border="0"〉〈/a〉   〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3213327/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Liu, Jie -- Renault, Ludovic -- Veaute, Xavier -- Fabre, Francis -- Stahlberg, Henning -- Heyer, Wolf-Dietrich -- CA92267/CA/NCI NIH HHS/ -- GM58015/GM/NIGMS NIH HHS/ -- U54 GM074929/GM/NIGMS NIH HHS/ -- U54 GM074929-05/GM/NIGMS NIH HHS/ -- U54GM74929/GM/NIGMS NIH HHS/ -- England -- Nature. 2011 Oct 23;479(7372):245-8. doi: 10.1038/nature10522.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Microbiology, University of California, Davis, Davis, California 95616-8665, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/22020281" target="_blank"〉PubMed〈/a〉
    Keywords: Adenosine Triphosphatases/genetics/*metabolism ; DNA Helicases/antagonists & inhibitors/*metabolism ; DNA Repair Enzymes/genetics/*metabolism ; DNA, Single-Stranded/chemistry/metabolism ; DNA-Binding Proteins/genetics/*metabolism ; Protein Binding ; Rad51 Recombinase/chemistry/*metabolism ; Saccharomyces cerevisiae/enzymology/genetics/*metabolism ; Saccharomyces cerevisiae Proteins/antagonists & ; inhibitors/chemistry/genetics/*metabolism
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 2
    Publication Date: 2010-12-28
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
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  • 3
    Publication Date: 2011-01-12
    Description: Homologous recombination (HR) is a key pathway to repair complex DNA damage, such as DNA gaps, double-strand breaks, and interstrand cross-links (1) (Fig. 1). Moreover, HR supports the recovery of stalled or broken replication forks and ensures faithful chromosome segregation during meiosis. The RAD52 gene in the budding yeast Saccharomyces cerevisiae encodes the lynchpin of HR in this organism. Hence, the genes of the HR pathway are called the RAD52 epistasis group. However, much to everybody's surprise, the RAD52 gene knockout in mice exhibits minimal to no phenotypes in recombination, repair, and meiosis (2). Instead, the breast and ovarian tumor...
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
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  • 4
    Publication Date: 2014-06-03
    Description: Mus81-Mms4/EME1 is a DNA structure-selective endonuclease that cleaves joint DNA molecules that form during homologous recombination in mitotic and meiotic cells. Here, we demonstrate by kinetic analysis using physically tethered DNA substrates that budding yeast Mus81-Mms4 requires inherent rotational flexibility in DNA junctions for optimal catalysis. Förster Resonance Energy Transfer experiments further reveal that recognition of 3'-flap and nicked Holliday junction substrates by Mus81-Mms4 involves induction of a sharp bend with a 100° angle between two duplex DNA arms. In addition, thiol crosslinking of Mus81-Mms4 bound to DNA junctions demonstrates that the heterodimer undergoes a conformational change induced by joint DNA molecules with preferred structural properties. The results from all three approaches suggest a model for catalysis by Mus81-Mms4 in which initial DNA binding is based on minimal structural requirements followed by a rate-limiting conformational transition of the substrate and protein. This leads to a sharply kinked DNA molecule that may fray the DNA four base pairs away from the junction point to position the nuclease for cleavage between the fourth and fifth nucleotide. These data suggest that mutually compatible conformational changes of Mus81-Mms4 and its substrates tailor its incision activity to nicked junction molecules.
    Print ISSN: 0305-1048
    Electronic ISSN: 1362-4962
    Topics: Biology
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  • 5
    Publication Date: 2013-05-04
    Description: The repair of DNA breaks by homologous recombination is a high-fidelity process, necessary for the maintenance of genome integrity. Thus, DNA synthesis associated with recombinational repair must be largely error-free. In this report, we show that human DNA polymerase delta () is capable of robust DNA synthesis at RAD51-mediated recombination intermediates dependent on the processivity clamp PCNA. Translesion synthesis polymerase eta () also extends these substrates, albeit far less processively. The single-stranded DNA binding protein RPA facilitates recombination-mediated DNA synthesis by increasing the efficiency of primer utilization, preventing polymerase stalling at specific sequence contexts, and overcoming polymerase stalling caused by topological constraint allowing the transition to a migrating D-loop. Our results support a model whereby the high-fidelity replicative DNA polymerase performs recombination-associated DNA synthesis, with translesion synthesis polymerases providing a supportive role as in normal replication.
    Print ISSN: 0305-1048
    Electronic ISSN: 1362-4962
    Topics: Biology
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