Abstract 2377: Atm-dependent recruitment of brd7 is required for transcriptional repression and repair at dna breaks flanking transcriptional active regions

Abstract

Abstract DNA double-strand break (DSB) is highly cytotoxic and deleterious lesions, causing gross chromosomal rearrangements, genomic instability and tumorigenesis (Meisenberg et al., 2019). In mammalian cells, such damages are mainly repaired through two pathways: non-homologous end joining (NHEJ) and homologous recombination (HR) (San Filippo et al., 2008). To avoid conflicts between ongoing transcription and repair activities, the DNA damage response (DDR) must coordinate the processes of repair signaling and local transcriptional capacity (Adam and Polo, 2014). Cells have evolved the ability of switching off transcription for DSB repair in ATM, DNA-PK and PARP1-dependent manner which is a critical step for maintaining genome-epigenome integrity (Iannelli et al., 2017; Shanbhag et al., 2010; Uckelmann and Sixma, 2017). The mono-ubiquitylation of H2A on K119 is one of the key determinants of transcriptional repression at sites of DNA damage (Kakarougkas et al., 2015; Rona et al., 2018; Shanbhag et al., 2010). However, depletion of these factors did not alleviate completely DSB-induced transcriptional repression, suggesting that additional yet unidentified factors or complexes are involved in the process. Here, we identified that BRD7, another specific subunit of PBAF complex, participated in DNA damage response (DDR) and was recruited to the damaged chromatin via ATM signaling. Mechanistically, BRD7 joined the polycomb repressive complex 2 (PRC2), the nucleosome remodeling and histone deacetylation (NuRD) complex at the damaged DNA and recruited E3 ubiquitin ligase RNF168 to the DSBs. Furthermore, ATM-mediated BRD7 phosphorylation is required for recruitment of the PRC2 complex, DSB sensor complex MRE11-RAD50-NBS1 (MRN) and RNF168 to the active transcription sites at DSBs, resulting in transcriptional repression and DNA repair. Moreover, BRD7 deficiency sensitized cancer cells to PARP inhibition. Collectively, BRD7 is crucial for DNA repair and DDR-mediated transcription repression, which may serve as a therapeutic target. Moreover, our findings have identified the missing link between DNA repair and transcription regulation that maintains genome integrity, as well as highlight the important role of PBAF complex in maintaining genomic integrity. Citation Format: Kaishun Hu. Atm-dependent recruitment of brd7 is required for transcriptional repression and repair at dna breaks flanking transcriptional active regions [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 2377.