Loss of BRCA1-A complex function in RAP80 null tumor cells.
Receptor Associated Protein 80 (RAP80) is a subunit of the BRCA1-A complex and targets BRCA1 to DNA damage sites in response to DNA double strand breaks. Since mutations of BRCA1 are associated with familial ovarian cancers, we screened 26 ovarian cancer-derived cell lines for RAP80 mutations and found that TOV-21G cells harbor a RAP80 mutation (c.1107G >A). This mutation generates a stop codon at Trp369, which deletes the partial AIR region and the C-terminal zinc fingers of RAP80. Interestingly, both the mutant and wild type alleles of RAP80 lose their expression due to promoter hypermethylation, suggesting that TOV-21G is a RAP80-null cell line. In these cells, not only is the BRCA1-A complex disrupted, but the relocation of the remaining subunits in the BRCA1-A complex including BRCA1, CCDC98, NBA1, BRCC36 and BRE is significantly suppressed. Moreover, TOV-21G cells are hypersensitive to ionizing radiation, which is due to the compromised DNA damage repair capacity in these cells. Reconstitution of TOV-21G cells with wild type RAP80 rescues these cellular defects in response to DNA damage. Thus, our results demonstrate that RAP80 is a scaffold protein in the BRCA1-A complex. Identification of TOV-21G as a RAP80 null tumor cell line will be very useful for the study of the molecular mechanism in DNA damage response.
Division of Molecular Medicine and Genetics, Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, Michigan, United States of America.
Chunjing
C
Bian
Rong
R
Wu
Kathleen
K
Cho
Xiaochun
X
Yu
D019313:BRCA1 Protein / Q000378:metabolism*; D002352:Carrier Proteins / Q000235:genetics* / Q000378:metabolism / Q000502:physiology; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000528:radiation effects; D053903:DNA Breaks, Double-Stranded; D004252:DNA Mutational Analysis; D004260:DNA Repair; D004268:DNA-Binding Proteins; D005260:Female; D056488:Histone Chaperones; D006801:Humans; D046912:Multiprotein Complexes / Q000378:metabolism; D009687:Nuclear Proteins / Q000235:genetics* / Q000378:metabolism / Q000502:physiology; D010051:Ovarian Neoplasms; D021122:Protein Subunits / Q000235:genetics / Q000378:metabolism
D019313:BRCA1 Protein; C492913:BRCA1 protein, human; D002352:Carrier Proteins; D004268:DNA-Binding Proteins; D056488:Histone Chaperones; D046912:Multiprotein Complexes; D009687:Nuclear Proteins; D021122:Protein Subunits; C466234:UIMC1 protein, human