title: The E3 ligase RNF8 regulates KU80 removal and NHEJ repair.
abstract: The ubiquitination cascade has a key role in the assembly of repair and signaling proteins at sites of double-strand DNA breaks. The E3 ubiquitin ligase RING finger protein 8 (RNF8) triggers the initial ubiquitination at double-strand DNA breaks, whereas sustained ubiquitination requires the downstream E3 ligase RING finger protein 168 (RNF168). It is not known whether RNF8 and RNF168 have discrete substrates and/or form different ubiquitin chains. Here we show that RNF168 acts with the ubiquitin-conjugating enzyme E2 13 (UBC13) and specifically synthesizes Lys63-linked chains, whereas RNF8 primarily forms Lys48-linked chains on chromatin, which promote substrate degradation. We also find that RNF8 regulates the abundance of the nonhomologous end-joining (NHEJ) repair protein KU80 at sites of DNA damage, and that RNF8 depletion results in prolonged retention of KU80 at damage sites and impaired nonhomologous end-joining repair. These findings reveal a distinct feature of RNF8 and indicate the involvement of the ubiquitination-mediated degradation pathway in DNA damage repair.
authors.affiliation: Department of Experimental Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas, USA.
authors.forename: Lin
authors.initials: L
authors.lastname: Feng
authors.forename: Junjie
authors.initials: J
authors.lastname: Chen
mesh_terms: D034961:Antigens, Nuclear / Q000378:metabolism*; D002843:Chromatin / Q000378:metabolism*; D059766:DNA End-Joining Repair; D004268:DNA-Binding Proteins / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D000072200:Ku Autoantigen; D008954:Models, Biological; D044767:Ubiquitin-Protein Ligases; D054875:Ubiquitination
chemical_list: D034961:Antigens, Nuclear; D002843:Chromatin; D004268:DNA-Binding Proteins; C486521:RNF8 protein, human; D044767:Ubiquitin-Protein Ligases; C000606509:Xrcc6 protein, human; D000072200:Ku Autoantigen