Department of Life Science, College of Natural Sciences, The Research Center for Cellular Homeostasis, Ewha Womans University, Seoul, Republic of Korea.
Oncogene. 2015 Jan 15;34(3):303-13. doi: 10.1038/onc.2013.556. Epub 2014 Jan 13.
ATP-dependent chromatin remodeling complexes such as SWI/SNF (SWItch/Sucrose NonFermentable) have been implicated in DNA double-strand break (DSB) repair and damage responses. However, the regulatory mechanisms that control the function of chromatin remodelers in DNA damage response are largely unknown. Here, we show that ataxia telangiectasia mutated (ATM) mediates the phosphorylation of BRG1, the catalytic ATPase of the SWI/SNF complex that contributes to DSB repair by binding γ-H2AX-containing nucleosomes via interaction with acetylated histone H3 and stimulating γ-H2AX formation, at Ser-721 in response to DNA damage. ATM-mediated phosphorylation of BRG1 occurs rapidly and transiently after DNA damage. Phosphorylated BRG1 binds γ-H2AX-containing nucleosomes to form the repair foci. The Ser-721 phosphorylation of BRG1 is critical for binding γ-H2AX-containing nucleosomes and stimulating γ-H2AX formation and DSB repair. BRG1 binds to acetylated H3 peptides much better after phosphorylation at Ser-721 by DNA damage. However, the phosphorylation of Ser-721 does not significantly affect the ATPase and transcriptional activities of BRG1. These results, establishing BRG1 as a novel and functional ATM substrate, suggest that the ATM-mediated phosphorylation of BRG1 facilitates DSB repair by stimulating the association of this remodeler with γ-H2AX nucleosomes via enhancing the affinity to acetylated H3. Our work also suggests that the mechanism of BRG1 stimulation of DNA repair is independent of the remodeler's enzymatic or transcriptional activities.
ATP 依赖的染色质重塑复合物，如 SWI/SNF（Switch/Sucrose NonFermentable），已被牵涉到 DNA 双链断裂（DSB）修复和损伤反应中。然而，控制染色质重塑剂在 DNA 损伤反应中功能的调控机制在很大程度上仍是未知的。在这里，我们显示出，ataxia telangiectasia 突变（ATM）介导了 BRG1 的磷酸化，BRG1 是 SWI/SNF 复合物的催化 ATP 酶，通过与乙酰化组蛋白 H3 的相互作用结合含有 γ-H2AX 的核小体，并刺激 γ-H2AX 的形成，从而有助于 DSB 修复，这一过程发生在 DNA 损伤时的 Ser-721 位点。ATM 介导的 BRG1 的磷酸化在 DNA 损伤后迅速而短暂地发生。磷酸化的 BRG1 结合含有 γ-H2AX 的核小体以形成修复焦点。BRG1 对含有 γ-H2AX 的核小体的结合和对 γ-H2AX 形成及 DSB 修复的刺激作用，对于 Ser-721 的磷酸化是关键的。在 DNA 损伤后通过 Ser-721 的磷酸化，BRG1 与乙酰化 H3 肽的结合能力大大增强。然而，Ser-721 的磷酸化对 BRG1 的 ATP 酶和转录活性没有显著影响。这些结果确定了 BRG1 作为一种新的和功能性的 ATM 底物，表明 ATM 介导的 BRG1 磷酸化通过增强与乙酰化 H3 的亲和力，促进该重塑剂与 γ-H2AX 核小体的结合，从而促进 DSB 修复。我们的工作还表明，BRG1 刺激 DNA 修复的机制独立于该重塑剂的酶或转录活性。
