Yan Qiongyu, Zhu Huiqin, Lan Li, Yi Jing, Yang Jie
Shanghai Key Laboratory of Tumor Microenvironment and Inflammation, Department of Biochemistry and Molecular Cell Biology, Institutes of Medical Sciences, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China.
University of Pittsburgh Cancer Institute, University of Pittsburgh School of Medicine,5117 Centre Avenue, Pittsburgh, PA 15213,USA; Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, 523 Bridgeside Point II, 450 Technology Drive, Pittsburgh, PA 15219, USA.
DNA Repair (Amst). 2017 Dec;60:18-28. doi: 10.1016/j.dnarep.2017.10.001. Epub 2017 Oct 10.
Non-homologous end-joining (NHEJ)-mediated repair of DNA double-strand breaks (DSBs) requires the formation of a Ku70/Ku80/DNA-PKcs complex at the DSB sites. A previous study has revealed Ku80 cleavage by caspase-3 during apoptosis. However, it remains largely unknown whether and how Ku80 cleavage affects its function in mediating NHEJ-mediated DNA repair. Here we report that Ku80 can be cleaved by caspases-2 at D726 upon a transient etoposide treatment. Caspase-2-mediated Ku80 cleavage promotes Ku80/DNA-PKcs interaction as the D726A mutation diminished Ku80 interaction with DNA-PKcs, while a Ku80 truncate (Ku80 ΔC6) lacking all the 6 residues following D726 rescued the weakened Ku80/DNA-PKcs interaction caused by caspase-2 knockdown. As a result, depletion or inhibition of caspase-2 impairs NHEJ-mediated DNA repair, and such impairment can be reversed by Ku80 ΔC6 overexpression. Taken together, our current study provides a novel mechanism for regulating NHEJ-mediated DNA repair, and sheds light on the function of caspase-2 in genomic stability maintenance.
DNA双链断裂（DSB）的非同源末端连接（NHEJ）介导的修复需要在DSB位点形成Ku70/Ku80/DNA-PKcs复合物。先前的一项研究揭示了凋亡过程中caspase-3对Ku80的切割。然而，Ku80切割是否以及如何影响其在介导NHEJ介导的DNA修复中的功能在很大程度上仍然未知。在此，我们报告在短暂的依托泊苷处理后，caspases-2可在D726位点切割Ku80。caspase-2介导的Ku80切割促进了Ku80/DNA-PKcs相互作用，因为D726A突变减少了Ku80与DNA-PKcs的相互作用，而缺失D726之后所有6个残基的Ku80截短体（Ku80ΔC6）挽救了由caspase-2敲低引起的减弱的Ku80/DNA-PKcs相互作用。因此，caspase-2的缺失或抑制会损害NHEJ介导的DNA修复，而这种损害可通过Ku80ΔC6的过表达来逆转。综上所述，我们目前的研究提供了一种调节NHEJ介导的DNA修复的新机制，并阐明了caspase-2在维持基因组稳定性中的功能。
