BRUCE regulates DNA double-strand break response by promoting USP8 deubiquitination of BRIT1.

The DNA damage response (DDR) is crucial for genomic integrity. BRIT1 (breast cancer susceptibility gene C terminus-repeat inhibitor of human telomerase repeat transcriptase expression), a tumor suppressor and early DDR factor, is recruited to DNA double-strand breaks (DSBs) by phosphorylated H2A histone family, member X (γ-H2AX), where it promotes chromatin relaxation by recruiting the switch/sucrose nonfermentable (SWI-SNF) chromatin remodeler to facilitate DDR. However, regulation of BRIT1 recruitment is not fully understood. The baculovirus IAP repeat (BIR)-containing ubiquitin-conjugating enzyme (BRUCE) is an inhibitor of apoptosis protein (IAP). Here, we report a non-IAP function of BRUCE in the regulation of the BRIT1-SWI-SNF DSB-response pathway and genomic stability. We demonstrate that BRIT1 is K63 ubiquitinated in unstimulated cells and that deubiquitination of BRIT1 is a prerequisite for its recruitment to DSB sites by γ-H2AX. We show mechanistically that BRUCE acts as a scaffold, bridging the ubiquitin-specific peptidase 8 (USP8) and BRIT1 in a complex to coordinate USP8-catalyzed deubiquitination of BRIT1. Loss of BRUCE or USP8 impairs BRIT1 deubiquitination, BRIT1 binding with γ-H2AX, the formation of BRIT1 DNA damage foci, and chromatin relaxation. Moreover, BRUCE-depleted cells display reduced homologous recombination repair, and BRUCE-mutant mice exhibit repair defects and genomic instability. These findings identify BRUCE and USP8 as two hitherto uncharacterized critical DDR regulators and uncover a deubiquitination regulation of BRIT1 assembly at damaged chromatin for efficient DDR and genomic stability.
Mesh Terms:
Animals, Cell Nucleus, Chromatin, Chromosomes, Mammalian, DNA Breaks, Double-Stranded, DNA Repair, Embryo, Mammalian, Endopeptidases, Endosomal Sorting Complexes Required for Transport, Fibroblasts, Genomic Instability, HEK293 Cells, Histones, Homologous Recombination, Humans, Inhibitor of Apoptosis Proteins, Lysine, Mice, Multiprotein Complexes, Nerve Tissue Proteins, Polyubiquitin, Protein Transport, Ubiquitin Thiolesterase, Ubiquitination
Proc. Natl. Acad. Sci. U.S.A. Mar. 17, 2015; 112(11);E1210-9 [PUBMED:25733871]
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