SET8 methyltransferase activity during the DNA double‐strand break response is required for recruitment of 53BP1

Abstract

DNA double-strand breaks (DSBs) activate a signaling pathway known as the DNA damage response (DDR) which via protein–protein interactions and post-translational modifications recruit signaling proteins, such as 53BP1, to chromatin flanking the lesion. Depletion of the SET8 methyltransferase prevents accumulation of 53BP1 at DSBs; however, this phenotype has been attributed to the role of SET8 in generating H4K20 methylation across the genome, which is required for 53BP1 binding to chromatin, prior to DNA damage. Here, we report that SET8 acts directly at DSBs during the DNA damage response (DDR). SET8 accumulates at DSBs and is enzymatically active at DSBs. Depletion of SET8 just prior to the induction of DNA damage abrogates 53BP1’s accumulation at DSBs, suggesting that SET8 acts during DDR. SET8’s occupancy at DSBs is regulated by histone deacetylases (HDACs). Finally, SET8 is functionally required for efficient repair of DSBs specifically via the non-homologous end-joining pathway (NHEJ). Our findings reveal that SET8’s active role during DDR at DSBs is required for 53BP1’s accumulation.

Histone modifications in DNA damage response

“…H4K20 methyltransferase MMSET (Wolf-Hirschhorn syndrome candidate 1) regulates the induction of H4K20 methylation on histones around double-strand breaks, which in turn facilitates 53BP1 recruitment (Hajdu et al, 2011;Pei et al, 2011). In addition to MMSET, another two H4K20 methyltransferases Set8 and Set9 are also responsible for H4K20 methylation and the recruitment of 53BP1 (Dulev et al, 2014;Greeson et al, 2008;Oda et al, 2010;Sanders et al, 2004;Yan et al, 2009). Similar to H3K79 methylation, H4K20 methylation recruits 53BP1 via its tandem Tudor domain as well (Botuyan et al, 2006).…”

DNA double strand break repair pathway choice: a chromatin based decision?

“…47 It is unclear whether or not H4K20 mono and/or dimethylation are efficiently induced at the vicinity of DSBs to recruit 53BP1. 43,[48][49][50][51][52] Interestingly, it has been suggested that DSB-induced alterations in chromatin structure could allow the specific unmasking of H4K20me1/2 at the vicinity of the break. 41,45 Similarly, DSB-induced eviction of H4K20me2 binding proteins, such as L3MBTL1 and JMJD2A/KDM4A, would also permit unmasking of the preexisting H4K20me1/ 2 marks, allowing for damage-induced 53BP1 recruitment.…”

Biological function and regulation of histone and non-histone lysine methylation in response to DNA damage

“…However, in Suv4-20h1-double-null MEFs, 53BP1 foci formation is delayed only in the early time of IR and recovered after 10 min [118] or not impaired [130]. Meanwhile, knockdown or knockout of PR-Set7/Set8, an H4K20me1 methyltransferase, severely impairs 53BP1 foci formation upon treatment with IR [115,130,131]. These results collectively indicate that the pre-existence of H4K20me1 by PR-Set7 is required for 53BP1 recruitment primarily in vivo.…”

“…These results collectively indicate that the pre-existence of H4K20me1 by PR-Set7 is required for 53BP1 recruitment primarily in vivo. In agreement with this, PR-Set7 is recruited to localized irradiation (405 nm UV laser) sites by proliferating cell nuclear antigen (PCNA) or to DSBs induced by AsiSI/I-SceI endonuclease in U2OS cells, which is dependent on Ku70, after which H4K20 is de novo methylated and 53BP1 is recruited [131][132][133]. Interestingly, it was reported that the rapid recruitment of PR-Set7 is not sufficient for 53BP1 recruitment.…”