Ubiquitin-specific protease 5 is required for the efficient repair of DNA double-strand breaks

During the DNA damage response (DDR), ubiquitination plays an important role in the recruitment and regulation of repair proteins. However, little is known about elimination of the ubiquitination signal after repair is completed. Here we show that the ubiquitin-specific protease 5 (USP5), a deubiquitinating enzyme, is involved in the elimination of the ubiquitin signal from damaged sites and is required for efficient DNA double-strand break (DSB) repair. Depletion of USP5 sensitizes cells to DNA damaging agents, produces DSBs, causes delayed disappearance of γH2AX foci after Bleocin treatment, and influences DSB repair efficiency in the homologous recombination pathway but not in the non-homologous end joining pathway. USP5 co-localizes to DSBs induced by laser micro-irradiation in a RAD18-dependent manner. Importantly, polyubiquitin chains at sites of DNA damage remained for longer periods in USP5-depleted cells. Our results show that disassembly of polyubiquitin chains by USP5 at sites of damage is important for efficient DSB repair. © 2014 Nakajima et al

A first update on mapping the human genetic architecture of COVID-19

peer reviewe

Involvement of the nuclear proteasome activator PA28 gamma in the cellular response to DNA double-strand breaks

The DNA damage response (DDR) is a complex signaling network that leads to damage repair while modulating numerous cellular processes. DNA double-strand breaks (DSBs)-a highly cytotoxic DNA lesion-activate this system most vigorously. The DSB response network is orchestrated by the ATM protein kinase, which phosphorylates key players in its various branches. Proteasome-mediated protein degradation plays an important role in the proteome dynamics following DNA damage induction. Here, we identify the nuclear proteasome activator PA28 gamma (REG gamma; PSME3) as a novel DDR player. PA28 gamma depletion leads to cellular radiomimetic sensitivity and a marked delay in DSB repair. Specifically, PA28 gamma deficiency abrogates the balance between the two major DSB repair pathways-nonhomologous end-joining and homologous recombination repair. Furthermore, PA28 gamma is found to be an ATM target, being recruited to the DNA damage sites and required for rapid accumulation of proteasomes at these sites. Our data reveal a novel ATM-PA28 gamma-proteasome axis of the DDR that is required for timely coordination of DSB repair

Is serum‐derived exosomal hTERT transcript a marker of oncogenic activity in primary brain tumors? An exploratory study

Abstract Background In order to proliferate indefinitely, all tumors require a telomere maintenance mechanism. The expression of human telomerase reverse transcriptase (hTERT) enables telomere maintenance and provides cancer cells with limitless replicative potential. As such, it may serve as an attractive biomarker for oncogenic activity. This study explored whether a liquid biopsy that analyses blood derived exosomal hTERT transcript (e‐hTERT‐trans) may serve as such a biomarker in gliomas and meningiomas when compared to healthy controls. Methods Exosomes were isolated from the pre‐operative sera of patients' samples stored in the biobank of both Rabin and Sheba Medical Centers. The levels of e‐hTERT‐trans were measured in 81 healthy controls, 117 meningiomas, 17 low‐grade gliomas, and 61 glioblastomas. Clinical parameters of the patients were collected retrospectively and compared to the levels of the e‐hTERT‐trans. Results The upper normal limit of controls e‐hTERT‐trans was 1.85 relative quantitation (RQ). The rate of detection increased with rising tumor grade and correlated with tumor recurrence in meningiomas: mean RQ without recurrence (2.17 ± 11.7) versus with recurrence (3.59 ± 4.42; p = 0.002). In glioblastomas, preoperative measurements correlated with tumor volume and with the disease course on serial sampling. Conclusions We demonstrated for the first time that the expression of e‐hTERT‐trans transcript can be measured in the serum of primary brain tumors. This exosomal marker carries the potential to serve as a biomarker once used in conjunction with other clinical and radiological parameters. Future studies are required to investigate whether the sensitivity could be augmented and whether it can be implemented into routine patients care

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

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

Mapping the human genetic architecture of COVID-19

The genetic make-up of an individual contributes to the susceptibility and response to viral infection. Although environmental, clinical and social factors have a role in the chance of exposure to SARS-CoV-2 and the severity of COVID-191,2, host genetics may also be important. Identifying host-specific genetic factors may reveal biological mechanisms of therapeutic relevance and clarify causal relationships of modifiable environmental risk factors for SARS-CoV-2 infection and outcomes. We formed a global network of researchers to investigate the role of human genetics in SARS-CoV-2 infection and COVID-19 severity. Here we describe the results of three genome-wide association meta-analyses that consist of up to 49,562 patients with COVID-19 from 46 studies across 19 countries. We report 13 genome-wide significant loci that are associated with SARS-CoV-2 infection or severe manifestations of COVID-19. Several of these loci correspond to previously documented associations to lung or autoimmune and inflammatory diseases3–7. They also represent potentially actionable mechanisms in response to infection. Mendelian randomization analyses support a causal role for smoking and body-mass index for severe COVID-19 although not for type II diabetes. The identification of novel host genetic factors associated with COVID-19 was made possible by the community of human genetics researchers coming together to prioritize the sharing of data, results, resources and analytical frameworks. This working model of international collaboration underscores what is possible for future genetic discoveries in emerging pandemics, or indeed for any complex human disease