Ubc13/Rnf8 ubiquitin ligases control foci formation of the Rap80/Abraxas/Brca1/Brcc36 complex in response to DNA damage.
The Brca1 A complex contains Brca1/Bard1, Abraxas, Rap80, and Brcc36; however, with the exception of the Brca1-Abraxas interaction, how the A complex is assembled is not known. The A complex is localized to sites of DNA damage through the UIM domains of RAP80, which bind K63-linked polyubiquitin chains. In this study, we identified an FHA domain RING finger E3 ubiquitin ligase, RNF8, and an E2-conjugating enzyme known to form K63-polyubiquitin chains, Ubc13, each of which is required to recruit the Brca1 A complex to sites of DNA damage. Rnf8 localizes to sites of DNA damage through an FHA-domain-containing region. We found that Rap80 contains an Abraxas interaction domain [AIR (Abraxas-interacting region)], required for association of Rap80 with Abraxas, Brca1, and Brcc36. Abraxas and Brcc36 associate through coiled-coil domains on each protein. These data suggest a model through which Ubc13 and Rnf8 are recruited to sites of DNA damage through DNA-damage-induced phosphorylation of a chromatin-associated protein and generate polyubiquitin chains that then recruit Rap80 and the entire Brca1 A complex to DNA-damage foci. This sequential E3 ubiquitin ligase recruitment constitutes a ubiquitin ligase cascade required for DNA repair and checkpoint signaling.
Wang
Bin
B
Department of Genetics, Howard Hughes Medical Institute, Center for Genetics and Genomics, Brigham and Women's Hospital, Harvard University Medical School, Boston, MA 02115, USA.
Elledge
Stephen J
SJ
D019313:BRCA1 Protein / Q000378:metabolism*; D002352:Carrier Proteins / Q000378:metabolism*; D045744:Cell Line, Tumor; D004249:DNA Damage; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000502:physiology*; D000072017:Deubiquitinating Enzymes; D015972:Gene Expression Regulation, Neoplastic; D006367:HeLa Cells; D056488:Histone Chaperones; D006801:Humans; D008565:Membrane Proteins / Q000378:metabolism*; D008954:Models, Biological; D008957:Models, Genetic; D009687:Nuclear Proteins / Q000378:metabolism*; D044763:Ubiquitin-Conjugating Enzymes / Q000737:chemistry / Q000502:physiology*; D044767:Ubiquitin-Protein Ligases
C520310:ABRAXAS1 protein, human; D019313:BRCA1 Protein; C492913:BRCA1 protein, human; D002352:Carrier Proteins; D004268:DNA-Binding Proteins; D056488:Histone Chaperones; D008565:Membrane Proteins; D009687:Nuclear Proteins; C486521:RNF8 protein, human; C466234:UIMC1 protein, human; C471607:UBE2N protein, human; D044763:Ubiquitin-Conjugating Enzymes; D044767:Ubiquitin-Protein Ligases; C518017:BRCC3 protein, human; D000072017:Deubiquitinating Enzymes