RAP80 acts independently of BRCA1 in repair of topoisomerase II poison-induced DNA damage.
The tumor suppressor BRCA1 functions in DNA homologous recombination, and mutations in BRCA1 increase the risk of breast and ovarian cancers. RAP80 is a component of BRCA1-containing complexes that is required for recruitment of BRCA1 to sites of DNA damage. To evaluate the role of RAP80 in DNA damage repair, we genetically disrupted both RAP80 alleles in the recombinogenic avian DT40 cell line. The resulting RAP80(-/-) cells were proficient at homologous recombination and nonhomologous end-joining (NHEJ), but were specifically sensitized to the topoisomerase II inhibitor etoposide. Notably, doubly mutant RAP80(-/-)BRCA1(-/-) cells were more sensitive to etoposide than were BRCA1(-/-) cells, revealing that RAP80 performs a BRCA1-independent repair function. Moreover, jointly impairing the function of CtIP, a distinct BRCA1 effector protein, rendered RAP80(-/-) cells more sensitive to etoposide compared with singly mutant cells, again illustrating a BRCA1-independent role of RAP80. Based on our findings, we propose that RAP80 exerts a specific function in repair of the topoisomerase-cleavage complex, such as the removal of covalently bound polypeptides from double-strand break ends independently of BRCA1.
Department of Radiation Genetics, Kyoto University, Graduate School of Medicine, Yoshidakonoe, Sakyo-ku, Kyoto, Japan.
Junko
J
Iijima
Zhihong
Z
Zeng
Shunichi
S
Takeda
Yoshihito
Y
Taniguchi
D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology; D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology; D019313:BRCA1 Protein / Q000502:physiology*; D002352:Carrier Proteins / Q000378:metabolism / Q000502:physiology*; D002460:Cell Line; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism / Q000528:radiation effects; D002645:Chickens; D002945:Cisplatin / Q000494:pharmacology; D004249:DNA Damage / Q000187:drug effects* / Q000528:radiation effects; D004260:DNA Repair / Q000187:drug effects* / Q000528:radiation effects; D004250:DNA Topoisomerases, Type II / Q000494:pharmacology*; D004268:DNA-Binding Proteins; D004706:Endodeoxyribonucleases; D005047:Etoposide / Q000494:pharmacology; D005260:Female; D005455:Fluorescent Antibody Technique; D005720:Gamma Rays; D056488:Histone Chaperones; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology; D009687:Nuclear Proteins / Q000378:metabolism / Q000502:physiology*; D016877:Oxidants / Q000494:pharmacology; D011995:Recombination, Genetic; D013347:Subcellular Fractions; D014466:Ultraviolet Rays
D000970:Antineoplastic Agents; D000972:Antineoplastic Agents, Phytogenic; D019313:BRCA1 Protein; D002352:Carrier Proteins; D004268:DNA-Binding Proteins; D056488:Histone Chaperones; D009687:Nuclear Proteins; D016877:Oxidants; C466234:UIMC1 protein, human; D005047:Etoposide; D006861:Hydrogen Peroxide; D004706:Endodeoxyribonucleases; C410741:RBBP8 protein, human; D004250:DNA Topoisomerases, Type II; D002945:Cisplatin