Division of Carcinogenesis and Cancer Prevention, National Cancer Center Research Institute, 5-1-1 Tsukiji, Chuo-ku, Tokyo 104-0045, Japan; Department of Biosciences, School of Science, Kitasato University, 1-15-1 Kitasato, Minami-ku, Sagamihara 252-0373, Japan.
Division of Carcinogenesis and Cancer Prevention, National Cancer Center Research Institute, 5-1-1 Tsukiji, Chuo-ku, Tokyo 104-0045, Japan; Biological Science and Technology, Tokyo University of Science, 6-1-1 Niijuku, Katsushika-ku, Tokyo 125-8585, Japan.
Cell Rep. 2015 Dec 29;13(12):2728-40. doi: 10.1016/j.celrep.2015.11.054. Epub 2015 Dec 17.
In response to DNA double-strand breaks (DSBs), H2AX is rapidly phosphorylated at Ser139 to promote DSB repair. Here we show that H2AX is rapidly stabilized in response to DSBs to efficiently generate γH2AX foci. This mechanism operated even in quiescent cells that barely expressed H2AX. H2AX stabilization resulted from the inhibition of proteasome-mediated degradation. Synthesized H2AX ordinarily underwent degradation through poly-ubiquitination mediated by the E3 ligase HUWE1; however, H2AX ubiquitination was transiently halted upon DSB formation. Such rapid H2AX stabilization by DSBs was associated with chromatin incorporation of H2AX and halting of its poly-ubiquitination mediated by the ATM kinase, the sirtuin protein SIRT6, and the chromatin remodeler SNF2H. H2AX Ser139, the ATM phosphorylation site, was essential for H2AX stabilization upon DSB formation. Our results reveal a pathway controlled by ATM, SIRT6, and SNF2H to block HUWE1, which stabilizes H2AX and induces its incorporation into chromatin only when cells are damaged.
针对 DNA 双链断裂 (DSBs)，H2AX 会迅速在丝氨酸 139 位磷酸化以促进 DSB 修复。本文中我们发现，H2AX 会迅速稳定以响应 DSB，从而有效地产生 γH2AX 焦点。该机制在几乎不表达 H2AX 的静止细胞中也能运行。H2AX 的稳定是通过蛋白酶体介导的降解来抑制的。合成的 H2AX 通常通过 E3 连接酶 HUWE1 介导的多泛素化进行降解；然而，在 DSB 形成时，H2AX 的泛素化会短暂停止。DSB 会迅速稳定 H2AX，这与 H2AX 与染色质的结合以及 ATM 激酶、SIRT6 蛋白和染色质重塑酶 SNF2H 介导的 H2AX 多泛素化的停止有关。H2AX 的丝氨酸 139 位是 ATM 磷酸化位点，对 DSB 形成时 H2AX 的稳定至关重要。我们的研究结果揭示了一条由 ATM、SIRT6 和 SNF2H 控制的途径，该途径可以阻断 HUWE1，HUWE1 只有在细胞受损时才会稳定 H2AX 并促使其整合到染色质中。
