title: Sequestration of mammalian Rad51-recombination protein into micronuclei.
abstract: The mammalian Rad51 protein is involved in homologous recombination and in DNA damage repair. Its nuclear distribution after DNA damage is highly dynamic, and distinct foci of Rad51 protein, distributed throughout the nuclear volume, are induced within a few hours after gamma irradiation; these foci then coalesce into larger clusters. Rad51-positive cells do not undergo DNA replication. Rad51 foci colocalize with both replication protein A and sites of unscheduled DNA repair synthesis and may represent a nuclear domain for recombinational DNA repair. By 24 h postirradiation, most foci are sequestered into micronuclei or assembled into Rad51-coated DNA fibers. These micronuclei and DNA fibers display genome fragmentation typical of apoptotic cell death. Other repair proteins, such as Rad52 and Gadd45, are not eliminated from the nucleus. DNA double strand breaks in repair-deficient cells or induced by the clastogen etoposide are also accompanied by the sequestering of Rad51 protein before cell death. The spindle poison colcemid causes cell cycle arrest and Rad51-foci formation without directly damaging DNA. Collectively, these observations suggest that mammalian Rad51 protein associates with damaged DNA and/or with DNA that is temporarily or irreversibly unable to replicate and these foci may subsequently be eliminated from the nucleus.
authors.affiliation: Max-Planck-Institute of Molecular Genetics, 14195 Berlin, Germany. haaf@mpimg-berlin-dahlem.mpg.de
authors.forename: T
authors.initials: T
authors.lastname: Haaf
authors.forename: E
authors.initials: E
authors.lastname: Raderschall
authors.forename: G
authors.initials: G
authors.lastname: Reddy
authors.forename: D C
authors.initials: DC
authors.lastname: Ward
authors.forename: C M
authors.initials: CM
authors.lastname: Radding
authors.forename: E I
authors.initials: EI
authors.lastname: Golub
mesh_terms: D016475:3T3 Cells; D000818:Animals; D002453:Cell Cycle; D002461:Cell Line, Transformed; D002467:Cell Nucleus; D004249:DNA Damage; D004260:DNA Repair; D004268:DNA-Binding Proteins / Q000378:metabolism*; D006801:Humans; D051379:Mice; D048629:Micronuclei, Chromosome-Defective / Q000378:metabolism*; D009153:Mutagens; D051135:Rad51 Recombinase; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D051716:Replication Protein A
chemical_list: D004268:DNA-Binding Proteins; D009153:Mutagens; C497167:RPA1 protein, human; D011993:Recombinant Fusion Proteins; D051716:Replication Protein A; C497168:Rpa1 protein, mouse; C495153:RAD51 protein, human; D051135:Rad51 Recombinase; C495154:Rad51 protein, mouse; C495155:Rad51 protein, rat