Department of Craniofacial Biology, School of Dental Medicine, University of Colorado Anschutz Medical Campus, Aurora, Colorado.
Department of Pharmacology, School of Medicine, University of Colorado Anschutz Medical Campus, Aurora, Colorado.
Mol Cancer Res. 2024 Feb 1;22(2):181-196. doi: 10.1158/1541-7786.MCR-23-0493.
Irradiation (IR) is a highly effective cancer therapy; however, IR damage to tumor-adjacent healthy tissues can result in significant comorbidities and potentially limit the course of therapy. We have previously shown that protein kinase C delta (PKCδ) is required for IR-induced apoptosis and that inhibition of PKCδ activity provides radioprotection in vivo. Here we show that PKCδ regulates histone modification, chromatin accessibility, and double-stranded break (DSB) repair through a mechanism that requires Sirtuin 6 (SIRT6). Overexpression of PKCδ promotes genomic instability and increases DNA damage and apoptosis. Conversely, depletion of PKCδ increases DNA repair via nonhomologous end joining (NHEJ) and homologous recombination (HR) as evidenced by increased formation of DNA damage foci, increased expression of DNA repair proteins, and increased repair of NHEJ and HR fluorescent reporter constructs. Nuclease sensitivity indicates that PKCδ depletion is associated with more open chromatin, while overexpression of PKCδ reduces chromatin accessibility. Epiproteome analysis reveals increased chromatin associated H3K36me2 in PKCδ-depleted cells which is accompanied by chromatin disassociation of KDM2A. We identify SIRT6 as a downstream mediator of PKCδ. PKCδ-depleted cells have increased SIRT6 expression, and depletion of SIRT6 reverses changes in chromatin accessibility, histone modification and DSB repair in PKCδ-depleted cells. Furthermore, depletion of SIRT6 reverses radioprotection in PKCδ-depleted cells. Our studies describe a novel pathway whereby PKCδ orchestrates SIRT6-dependent changes in chromatin accessibility to regulate DNA repair, and define a mechanism for regulation of radiation-induced apoptosis by PKCδ.
PKCδ controls sensitivity to irradiation by regulating DNA repair.
辐射（IR）是一种非常有效的癌症治疗方法；然而，IR 对肿瘤邻近健康组织的损伤会导致严重的合并症，并可能限制治疗过程。我们之前已经表明，蛋白激酶 C 三角洲（PKCδ）是 IR 诱导细胞凋亡所必需的，并且抑制 PKCδ 活性可以在体内提供放射保护。在这里，我们表明 PKCδ 通过需要 Sirtuin 6（SIRT6）的机制调节组蛋白修饰、染色质可及性和双链断裂（DSB）修复。PKCδ 的过表达会促进基因组不稳定性，并增加 DNA 损伤和细胞凋亡。相反，PKCδ 的耗竭会通过非同源末端连接（NHEJ）和同源重组（HR）增加 DNA 修复，这表现在 DNA 损伤焦点的形成增加、DNA 修复蛋白的表达增加以及 NHEJ 和 HR 荧光报告构建体的修复增加。核酸酶敏感性表明 PKCδ 耗竭与更开放的染色质有关，而 PKCδ 的过表达会降低染色质可及性。Epiproteome 分析显示，PKCδ 耗竭细胞中与染色质相关的 H3K36me2 增加，同时伴随 KDM2A 染色质解离。我们确定 SIRT6 是 PKCδ 的下游介质。PKCδ 耗竭细胞中 SIRT6 的表达增加，并且 SIRT6 的耗竭逆转了 PKCδ 耗竭细胞中染色质可及性、组蛋白修饰和 DSB 修复的变化。此外，SIRT6 的耗竭逆转了 PKCδ 耗竭细胞中的放射保护作用。我们的研究描述了一种新的途径，其中 PKCδ 通过调节染色质可及性来协调 SIRT6 依赖性的 DNA 修复，并且定义了 PKCδ 调节辐射诱导细胞凋亡的机制。
PKCδ 通过调节 DNA 修复来控制对辐射的敏感性。
