title: The UBC Domain Is Required for BRUCE to Promote BRIT1/MCPH1 Function in DSB Signaling and Repair Post Formation of BRUCE-USP8-BRIT1 Complex.
abstract: BRUCE is implicated in the regulation of DNA double-strand break response to preserve genome stability. It acts as a scaffold to tether USP8 and BRIT1, together they form a nuclear BRUCE-USP8-BRIT1 complex, where BRUCE holds K63-ubiquitinated BRIT1 from access to DSB in unstressed cells. Following DSB induction, BRUCE promotes USP8 mediated deubiquitination of BRIT1, a prerequisite for BRIT1 to be released from the complex and recruited to DSB by binding to γ-H2AX. BRUCE contains UBC and BIR domains, but neither is required for the scaffolding function of BRUCE mentioned above. Therefore, it remains to be determined whether they are required for BRUCE in DSB response. Here we show that the UBC domain, not the BIR domain, is required for BRUCE to promote DNA repair at a step post the formation of BRUCE-USP8-BRIT1 complex. Mutation or deletion of the BRUCE UBC domain did not disrupt the BRUCE-USP8-BRIT1 complex, but impaired deubiquitination and consequent recruitment of BRIT1 to DSB. This leads to impaired chromatin relaxation, decreased accumulation of MDC1, NBS1, pATM and RAD51 at DSB, and compromised homologous recombination repair of DNA DSB. These results demonstrate that in addition to the scaffolding function in complex formation, BRUCE has an E3 ligase function to promote BRIT1 deubiquitination by USP8 leading to accumulation of BRIT1 at DNA double-strand break. These data support a crucial role for BRUCE UBC activity in the early stage of DSB response.
authors.affiliation: Department of Cancer and Cell Biology, University of Cincinnati, College of Medicine, Cincinnati, OH, 45267, United States of America.
authors.forename: Chunmin
authors.initials: C
authors.lastname: Ge
authors.affiliation: Department of Cancer and Cell Biology, University of Cincinnati, College of Medicine, Cincinnati, OH, 45267, United States of America.
authors.forename: Lixiao
authors.initials: L
authors.lastname: Che
authors.affiliation: Department of Cancer and Cell Biology, University of Cincinnati, College of Medicine, Cincinnati, OH, 45267, United States of America.
authors.forename: Chunying
authors.initials: C
authors.lastname: Du
mesh_terms: D018797:Cell Cycle Proteins; D002460:Cell Line; D002843:Chromatin / Q000502:physiology; D003598:Cytoskeletal Proteins; D053903:DNA Breaks, Double-Stranded; D004260:DNA Repair; D010450:Endopeptidases / Q000378:metabolism*; D056827:Endosomal Sorting Complexes Required for Transport / Q000378:metabolism*; D057809:HEK293 Cells; D006801:Humans; D051034:Inhibitor of Apoptosis Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D015398:Signal Transduction; D043222:Ubiquitin Thiolesterase / Q000378:metabolism*; D054875:Ubiquitination
chemical_list: C401541:BIRC6 protein, human; D018797:Cell Cycle Proteins; D002843:Chromatin; D003598:Cytoskeletal Proteins; D056827:Endosomal Sorting Complexes Required for Transport; D051034:Inhibitor of Apoptosis Proteins; C460645:MCPH1 protein, human; D009419:Nerve Tissue Proteins; D010450:Endopeptidases; C541534:USP8 protein, human; D043222:Ubiquitin Thiolesterase