Ubc13/Rnf8 ubiquitin ligases control foci formation of the Rap80/Abraxas/Brca1/Brcc36 complex in response to DNA damage
- Department of Genetics, Howard Hughes Medical Institute, Center for Genetics and Genomics, Brigham and Women's Hospital, Harvard University Medical School, Boston, MA 02115
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Contributed by Stephen J. Elledge, October 22, 2007 (received for review October 12, 2007)
Abstract
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.
Footnotes
- *To whom correspondence should be addressed at: Department of Genetics, Center for Genetics and Genomics, Howard Hughes Medical Institute, Room 158D, New Research Building, Harvard University Medical School, 77 Avenue Louis Pasteur, Boston, MA 02115. E-mail: selledge{at}genetics.med.harvard.edu
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Author contributions: B.W. and S.J.E. designed research; B.W. performed research; B.W. analyzed data; and B.W. and S.J.E. wrote the paper.
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The authors declare no conflict of interest.
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See Commentary on page 20645.
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This article contains supporting information online at www.pnas.org/cgi/content/full/0710061104/DC1.
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Freely available online through the PNAS open access option.
- © 2007 by The National Academy of Sciences of the USA
