TAILIEUCHUNG - Báo cáo khoa học: DNA mediated disassembly of hRad51 and hRad52 proteins and recruitment of hRad51 to ssDNA by hRad52

Purified human Rad51 and Rad52 proteins exhibit multiple oligomeric states, in vitro. Single-stranded DNA (ssDNA) renders high molecular weight aggregates of both proteins into smaller and soluble forms that include even the monomers. Consequently, these proteins that have a pro-pensity to interact with each other’s higher order forms by themselves, start interacting with monomeric forms in the presence of ssDNA, presumably reflecting the steps of protein assembly on DNA. | ềFEBS Journal DNA mediated disassembly of hRad51 and hRad52 proteins and recruitment of hRad51 to ssDNA by hRad52 Vasundhara M. Navadgi Ashish Shukla Rahul Kumar Vempati and Basuthkar J. Rao Department of BiologicalSciences Tata Institute of FundamentalResearch Mumbai India Keywords DNA binding homologous recombination oligomerization Rad51 Rad52 Correspondence . Rao Department of Biological Sciences Tata Institute of Fundamental Research Homi Bhabha Road Colaba Mumbai 400 005 India Fax 91 22 22782606 22782255 Tel 91 22 22804545 Extn 2606 Purified human Rad51 and Rad52 proteins exhibit multiple oligomeric states in vitro. Single-stranded DNA ssDNA renders high molecular weight aggregates of both proteins into smaller and soluble forms that include even the monomers. Consequently these proteins that have a propensity to interact with each other s higher order forms by themselves start interacting with monomeric forms in the presence of ssDNA presumably reflecting the steps of protein assembly on DNA. In the same conditions DNA binding assays reveal hRad52-mediated recruitment of hRad51 on ssDNA. Put together these studies hint at DNA-induced disassembly of higher-order forms of Rad51 and Rad52 proteins as steps that precede protein assembly during hRad51 presynapsis on DNA in vitro. Received 1 October 2005 accepted 10 November 2005 doi Human Rad51 protein hRad51 a homologue of Escherichia coli RecA performs the fundamental role of homologous pairing and strand exchange during homologous recombination and double-strand break repair 1 2 . Rad51 and Rad52 colocalize in distinct nuclear foci in response to DNA damage 3 . Yeast rad52 mutants show extensive degradation of the DNA double-strand break ends suggesting that Rad52 is critically involved in stable maintenance of chromosomal integrity 4 . Cytological studies indicate that Rad52 is required for Rad51 foci formation during meiosis 5 and chromatin immunoprecipitation assays .

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