ASF1a Promotes Non-homologous End Joining Repair by Facilitating Phosphorylation of MDC1 by ATM at Double-Strand Breaks

• Published in: Molecular cell 2017-10, Vol.68 (1), p.61-75.e5
• Main Authors: Lee, Kyung Yong, Im, Jun-Sub, Shibata, Etsuko, Dutta, Anindya
• Format: Article
• Language: English
• Subjects: 53BP1; Adaptor Proteins, Signal Transducing; ASF1a; Ataxia Telangiectasia Mutated Proteins - genetics; Ataxia Telangiectasia Mutated Proteins - metabolism; ATM; Cell Cycle Proteins - genetics; Cell Cycle Proteins - metabolism; Cell Line, Transformed; Cell Line, Tumor; Chromatin - chemistry; Chromatin - metabolism; DNA - genetics; DNA - metabolism; DNA Breaks, Double-Stranded; DNA End-Joining Repair; DNA, Neoplasm - genetics; DNA, Neoplasm - metabolism; DNA-Binding Proteins - genetics; DNA-Binding Proteins - metabolism; Gene Deletion; Gene Expression Regulation, Neoplastic; HEK293 Cells; HeLa Cells; histone; Histones - genetics; Histones - metabolism; Humans; MDC1; Molecular Chaperones; NHEJ; Nuclear Proteins - genetics; Nuclear Proteins - metabolism; Phosphorylation; RNF168; RNF8; Signal Transduction; Trans-Activators - genetics; Trans-Activators - metabolism; Tumor Suppressor p53-Binding Protein 1 - genetics; Tumor Suppressor p53-Binding Protein 1 - metabolism; Ubiquitin - genetics; Ubiquitin - metabolism; Ubiquitin-Protein Ligases - genetics; Ubiquitin-Protein Ligases - metabolism; Ubiquitination
• ISSN: 1097-2765; 1097-4164
• DOI: 10.1016/j.molcel.2017.08.021

Double-strand breaks (DSBs) of DNA in eukaryotic cells are predominantly repaired by non-homologous end joining (NHEJ). The histone chaperone anti-silencing factor 1a (ASF1a) interacts with MDC1 and is recruited to sites of DSBs to facilitate the interaction of phospho-ATM with MDC1 and phosphorylation of MDC1, which are required for the recruitment of RNF8/RNF168 histone ubiquitin ligases. Thus, ASF1a deficiency reduces histone ubiquitination at DSBs, decreasing the recruitment of 53BP1, and decreases NHEJ, rendering cells more sensitive to DSBs. This role of ASF1a in DSB repair cannot be provided by the closely related ASF1b and does not require its histone chaperone activity. Homozygous deletion of ASF1A is seen in 10%–15% of certain cancers, suggesting that loss of NHEJ may be selected in some malignancies and that the deletion can be used as a molecular biomarker for cancers susceptible to radiotherapy or to DSB-inducing chemotherapy. [Display omitted] •ASF1a, which can be homozygously deleted in cancers, promotes NHEJ and suppresses HR•ASF1a interacts with MDC1 to facilitate the latter’s interaction with activated ATM•ASF1a thus promotes phosphorylation of MDC1 and the recruitment of RNF8 to DSBs•ASF1a is essential for histone ubiquitination and 53BP1 recruitment at DSBs and NHEJ Lee et al. show that ASF1a, independent of its histone chaperone role, promotes NHEJ repair at double-strand breaks by facilitating the interaction of MDC1 with activated ATM for histone ubiquitination-dependent recruitment of repair factors.