The Preston Robert Tisch Brain Tumor Center, Duke University Medical Center, Durham, NC 27710, USA; Department of Pathology, Duke University Medical Center, Durham, NC 27710, USA; Gastrointestinal Cancer Center, Peking University Cancer Hospital, Beijing 100142, China.
The Preston Robert Tisch Brain Tumor Center, Duke University Medical Center, Durham, NC 27710, USA; Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC 27710, USA.
Cell Rep. 2019 Sep 17;28(12):3199-3211.e5. doi: 10.1016/j.celrep.2019.08.031.
H2AX safeguards genomic stability in a dose-dependent manner; however, mechanisms governing its proteostasis are poorly understood. Here, we identify a PRMT5-RNF168-SMURF2 cascade that regulates H2AX proteostasis. We show that PRMT5 sustains the expression of RNF168, an E3 ubiquitin ligase essential for DNA damage response (DDR). Suppression of PRMT5 occurs in methylthioadenosine phosphorylase (MTAP)-deficient glioblastoma cells and attenuates the expression of RNF168, leading to destabilization of H2AX by E3 ubiquitin ligase SMURF2. RNF168 and SMURF2 serve as a stabilizer and destabilizer of H2AX, respectively, via their dynamic interactions with H2AX. In supporting an important role of this signaling cascade in regulating H2AX, MTAP-deficient glioblastoma cells display higher levels of DNA damage spontaneously or in response to genotoxic agents. These findings reveal a regulatory mechanism of H2AX proteostasis and define a signaling cascade that is essential to DDR and that is disrupted by the loss of a metabolic enzyme in tumor cells.
H2AX 以剂量依赖的方式保护基因组稳定性；然而，其蛋白质稳定的机制仍知之甚少。在这里，我们发现了一个 PRMT5-RNF168-SMURF2 级联反应，它调节 H2AX 的蛋白质稳定。我们表明，PRMT5 维持 RNF168 的表达，RNF168 是 DNA 损伤反应（DDR）所必需的 E3 泛素连接酶。甲基硫腺苷磷酸酶（MTAP）缺陷型脑胶质瘤细胞中发生 PRMT5 抑制，导致 RNF168 表达减弱，从而导致 E3 泛素连接酶 SMURF2 使 H2AX 不稳定。RNF168 和 SMURF2 通过与 H2AX 的动态相互作用，分别作为 H2AX 的稳定剂和失稳剂。支持这种信号级联在调节 H2AX 中起重要作用，MTAP 缺陷型脑胶质瘤细胞在自发或对遗传毒性药物反应时显示出更高水平的 DNA 损伤。这些发现揭示了 H2AX 蛋白质稳定的调节机制，并定义了一个信号级联，该级联对于 DDR 是必不可少的，并且在肿瘤细胞中代谢酶的缺失会破坏该信号级联。
