The ubiquitin E3/E4 ligase, UBE4A, fine-tunes protein ubiquitylation and accumulation at sites of DNA damage facilitating double-strand break repair

Double-strand breaks (DSBs) are critical DNA lesions that robustly activate the elaborate DNA damage response (DDR) network. We identified a critical player in DDR fine-tuning - the E3/E4 ubiquitin ligase, UBE4A. UBE4A’s recruitment to sites of DNA damage is dependent on primary E3 ligases in the DDR and promotes enhancement and sustainment of K48- and K63-linked ubiquitin chains at these sites. This step is required for timely recruitment of the RAP80 and BRCA1 proteins and proper organization of RAP80- and BRCA1-associated protein complexes at DSB sites. This pathway is essential for optimal end-resection at DSBs, and its abrogation leads to up-regulation of the highly mutagenic alternative end-joining repair at the expense of error-free homologous recombination repair. Our data uncover a critical regulatory level in the DSB response and underscore the importance of fine-tuning of the complex DDR network for accurate and balanced execution of DSB repai

The ubiquitin E3/E4 ligase UBE4A adjusts protein ubiquitylation and accumulation at sites of DNA damage, facilitating double-strand break repair

Double-strand breaks (DSBs) are critical DNA lesions that robustly activate the elaborate DNA damage response (DDR) network. We identified a critical player in DDR fine-tuning: the E3/E4 ubiquitin ligase UBE4A. UBE4A’s recruitment to sites of DNA damage is dependent on primary E3 ligases in the DDR and promotes enhancement and sustainment of K48- and K63-linked ubiquitin chains at these sites. This step is required for timely recruitment of the RAP80 and BRCA1 proteins and proper organization of RAP80- and BRCA1-associated protein complexes at DSB sites. This pathway is essential for optimal end resection at DSBs, and its abrogation leads to upregulation of the highly mutagenic alternative end-joining repair at the expense of error-free homologous recombination repair. Our data uncover a critical regulatory level in the DSB response and underscore the importance of fine-tuning the complex DDR network for accurate and balanced execution of DSB repair.Work in the Y.S. laboratory is funded by research grants from the Dr. Miriam and Sheldon G. Adelson Medical Research Foundation, the A-T Children’s Project, the Israel Science Foundation Joint ISF-NSFC Research Program (jointly funded by the Israel Science Foundation and the National Natural Science Foundation of China - Grant No. 998/14), and the Israel Cancer Research Fund (Professorship). T.M. and T.C.V. were supported by funding from the Intramural Research Program of the National Institutes of Health (NIH), National Cancer Institute, and the Center for Cancer Research. Work in the K.R. laboratory is supported by the Swiss National Science Foundation (31003A_141197) and the Medical Research Council, UK (MC_PC_12001/1). Work in the G.D. laboratory is supported by a discovery grant from the Natural Sciences and Engineering Research Council of Canada (RGPIN 05616). Work in the P.H. lab was supported by an R+D+I grant from the Spanish Ministry of Economy and Competitivity (SAF2013-43255-P) and an ERC starting grant (DSBRECA). Work in the E.R. laboratory is supported by NIH grants GM108119 and CA187612 and American Cancer Society grant ACS130304-RSG-16-241-01-DMC. I.S.-B. is the recipient of a Ph.D. fellowship from the University of Sevilla. D.C. was supported by a Nova Scotia graduate scholarship. K.B.B. is a Jack and Florence Berlin fellow. Y.S. is a Research Professor of the Israel Cancer Research Fund.Peer reviewe

UBQLN4 Represses Homologous Recombination and Is Overexpressed in Aggressive Tumors

Genomic instability can be a hallmark of both human genetic disease and cancer. We identify a deleterious UBQLN4 mutation in families with an autosomal recessive syndrome reminiscent of genome instability disorders. UBQLN4 deficiency leads to increased sensitivity to genotoxic stress and delayed DNA double-strand break (DSB) repair. The proteasomal shuttle factor UBQLN4 is phosphorylated by ATM and interacts with ubiquitylated MRE11 to mediate early steps of homologous recombination-mediated DSB repair (HRR). Loss of UBQLN4 leads to chromatin retention of MRE11, promoting non-physiological HRR activity in vitro and in vivo. Conversely, UBQLN4 overexpression represses HRR and favors non-homologous end joining. Moreover, we find UBQLN4 overexpressed in aggressive tumors. In line with an HRR defect in these tumors, UBQLN4 overexpression is associated with PARP1 inhibitor sensitivity. UBQLN4 therefore curtails HRR activity through removal of MRE11 from damaged chromatin and thus offers a therapeutic window for PARP1 inhibitor treatment in UBQLN4-overexpressing tumors.Control of MRE11 association with chromatin by UBQLN4 during double-strand break repair influences repair pathway choice and can be dysregulated in tumorigenesis.This work was funded through the Dr. M. and S.G. Adelson Medical Research Foundation, The Israel Science Foundation joint ISF-NSFC Research Program and The Israel Cancer Research Fund (to Y.S.), the German-Israeli Foundation for Research and Development (I-65-412.20-2016 to Y.S. and H.C.R.), the Deutsche Forschungsgemeinschaft (KFO-286-RP2 to H.C.R., KFO-286-CP2 to M.P., JA2439/1-1 to R.D.J., DI1731/2-1 to F.D.), the Else Kröner-Fresenius Stiftung (2014-A06 to H.C.R., 2016_Kolleg.19 to R.D.J.), the Deutsche Krebshilfe (1117240 to H.C.R. and the Mildred-Scheel Professorship to M.P.), the German Ministry of Education and Research (BMBF 01GM1211B to D.W., BMBF e:Med 01ZX1303A and 01ZX1406 to M.P., BMBF e:Med 01ZX1303 and 01ZX1307 to M.F.), and R+D+I grants from the Spanish Ministry of Economy and Competitivity (SAF2013-43255-P and SAF2016-74855-P to P.H.). Y.S. is a Research Professor of the Israel Cancer Research Fund