title: Sub-nuclear localization of Rad51 in response to DNA damage.
abstract: The repair of DNA double-strand breaks involves the accumulation of key homologous recombination proteins in nuclear foci at the sites of repair. The organization of these foci in relation to non-chromatin nuclear structures is poorly understood. To address this question, we examined the distribution of several recombination proteins in subcellular fractions following treatment of HeLa cells with ionizing radiation and the crosslinking agent mitomycin C. The results showed association of Rad51, Rad54, BRCA1 and BRCA2, but not Rad51C, with the nuclear matrix fraction in response to double-strand breaks induction. The association of Rad51 with the nuclear matrix correlates with the formation of Rad51 nuclear foci as a result of DNA damage. Fractionation in situ confirmed that Rad51 foci remained firmly immobilized within the chromatin-depleted nuclei. Irs1SF cells that are unable to form Rad51 damage-induced nuclear foci did not show accumulation of Rad51 in the nuclear matrix. Similarly, no accumulation of Rad51 in the nuclear matrix could be observed after treatment of HeLa cells with the kinase inhibitor caffeine, which reduces formation of Rad51 foci. The results were compared to the distribution of the phosphorylated histone variant, gamma-H2AX. These data suggest a dynamic association and tethering of recombination proteins and surrounding chromatin regions to the nuclear matrix.
authors.affiliation: Institute of Molecular Biology, Bulgarian Academy of Sciences, Sofia 1113, Bulgaria.
authors.forename: Emil
authors.initials: E
authors.lastname: Mladenov
authors.forename: Boyka
authors.initials: B
authors.lastname: Anachkova
authors.forename: Irina
authors.initials: I
authors.lastname: Tsaneva
mesh_terms: D000818:Animals; D019313:BRCA1 Protein / Q000378:metabolism; D024682:BRCA2 Protein / Q000378:metabolism; D016466:CHO Cells; D002458:Cell Fractionation; D002467:Cell Nucleus / Q000201:enzymology*; D002843:Chromatin / Q000378:metabolism; D006224:Cricetinae; D004249:DNA Damage / Q000528:radiation effects; D004265:DNA Helicases; D004260:DNA Repair; D004268:DNA-Binding Proteins / Q000378:metabolism; D003850:Deoxyribonuclease I / Q000378:metabolism / Q000494:pharmacology; D006367:HeLa Cells; D006657:Histones / Q000378:metabolism; D006801:Humans; D008856:Microscopy, Fluorescence; D016685:Mitomycin / Q000378:metabolism / Q000494:pharmacology; D015530:Nuclear Matrix / Q000378:metabolism; D009687:Nuclear Proteins / Q000378:metabolism; D017830:Octoxynol / Q000378:metabolism / Q000494:pharmacology; D051135:Rad51 Recombinase / Q000032:analysis* / Q000378:metabolism; D011839:Radiation, Ionizing
chemical_list: D019313:BRCA1 Protein; D024682:BRCA2 Protein; D002843:Chromatin; D004268:DNA-Binding Proteins; C468783:H2AX protein, human; D006657:Histones; D009687:Nuclear Proteins; C448305:RAD51C protein, human; D016685:Mitomycin; D017830:Octoxynol; D051135:Rad51 Recombinase; D003850:Deoxyribonuclease I; D004265:DNA Helicases; C103532:RAD54L protein, human