DNA双链断裂(DSB)被认为是最有害的DNA损伤形式之一。这些DSB通过非同源末端连接(NHEJ)和同源重组(HR)途径修复,并且这些过程中的缺陷可导致基因组不稳定并促进肿瘤发生。磷酸酶和Tensin同源物(PTEN)在HR修复中至关重要。然而,它在NHEJ修复途径中的参与仍然难以捉摸。在这项研究中,我们研究了PTEN在NHEJ修复途径中的表观遗传调控功能。我们的发现表明,PTEN的磷酸化和磷酸酶活性都是有效的NHEJ介导的DSB修复所必需的。在DNA损伤反应中,我们观察到关键NHEJ蛋白的表达和染色质附着减少,包括Ku70/80,DNA-PKcs,XRCC4和XLF,在PTEN-null单元格中。这种减少归因于这些NHEJ蛋白的不稳定性,正如我们的蛋白质半衰期测定所证实的。我们已经证明了DNA-PKcs抑制剂,NU7026抑制DNA损伤诱导的PTENC末端磷酸化。因此,我们的研究表明PTEN可能是DNA-PKcs的靶标。蛋白质-蛋白质对接分析还显示PTEN与DNA-PKcs的C末端区域相互作用。PTEN无效细胞在DNA损伤后表现出受损的DNA-PKcs灶,因为它处于超磷酸化状态。磷酸化-PTEN通过维持其也取决于其磷酸酶活性的低磷酸化状态来帮助在DNA损伤位点上募集DNA-PKcs。因此,DNA损伤后,PTEN和DNA-PKcs之间的串扰调节NHEJ途径。因此,在DNA损伤期间,PTEN被DNA-PKcs直接或间接磷酸化并附着在染色质上,导致DNA-PKcs去磷酸化,随后在染色质上募集其他NHEJ因子,以有效执行NHEJ途径。因此,我们的研究提供了对PTEN的表观遗传调控及其在控制NHEJ途径中的重要作用的分子理解.
DNA double-strand breaks (DSBs) are considered one of the most harmful forms of DNA damage. These DSBs are repaired through non-homologous end joining (NHEJ) and homologous recombination (HR) pathways and defects in these processes can lead to genomic instability and promote tumorigenesis. Phosphatase and Tensin homolog (PTEN) are crucial in HR repair. However, its involvement in the NHEJ repair pathway has remained elusive. In this study, we investigate the function of epigenetic regulation of PTEN in the NHEJ repair pathway. Our findings indicate that both the phosphorylation and phosphatase activity of PTEN are required for efficient NHEJ-mediated DSB repair. During the DNA damage response, we observed a reduced expression and chromatin attachment of the key NHEJ proteins, including Ku70/80, DNA-PKcs, XRCC4, and XLF, in PTEN-null cells. This reduction was attributed to the instability of these NHEJ proteins, as confirmed by our protein half-life assay. We have demonstrated that the DNA-PKcs inhibitor, NU7026, suppresses the DNA damage-induced phosphorylation of the C-terminal of PTEN. Thus, our study indicates that PTEN could be a target of DNA-PKcs. Protein-protein docking analysis also shows that PTEN interacts with the C-terminal region of DNA-PKcs. PTEN null cells exhibit compromised DNA-PKcs foci after DNA damage as it is in a hyper-phosphorylated state. Phospho-PTEN assists in recruiting DNA-PKcs on the DNA damage site by maintaining its hypo-phosphorylated state which also depends on its phosphatase activity. Therefore, after DNA damage, crosstalk between PTEN and DNA-PKcs modulates the NHEJ pathway. Thus, during DNA damage, PTEN gets phosphorylated directly or indirectly by DNA-PKcs and attaches to chromatin, resulting in the dephosphorylation of DNA-PKcs and subsequently recruitment of other NHEJ factors on chromatin occurs for efficient execution of the NHEJ pathway. Thus, our research provides a molecular understanding of the epigenetic regulation of PTEN and its significant role in controlling the NHEJ pathway.