SIK2与DNA-PKcs相互作用调节放射损伤细胞的G2/M阻滞与纺锤体结构稳定性

DNA依赖蛋白激酶催化亚基（DNA-PKcs）是哺乳动物细胞DNA双链断裂非同源末端连接修复中的关键激酶。我们最近发现DNA-PKcs具有调节放射损伤细胞的有丝分裂进程、中心体和纺锤体结构稳定性的功能。进一步通过酵母双杂交技术发现DNA-PKcs与盐诱导激酶2 (SIK2) 有相互作用。而SIK2也参与调控中心体分离和双极纺锤体形成。本课题将首先确定SIK2与DNA-PKcs相互作用的细胞周期时相相关性，并鉴定其相互作用位点；通过体外磷酸化实验确定SIK2为DNA-PKcs的磷酸化底物及其磷酸化位点，验证DNA-PKcs对SIK2体内磷酸化调节作用及与细胞周期进程关系；研究DNA-PKc通过磷酸化SIK2对中心体分离、纺锤体结构及有丝分裂进程的影响。通过此研究将揭示放射损伤细胞G2/M期阻滞和纺锤体结构稳定性新机制，这对全面揭示放射损伤诱发的细胞学反应和基因组稳定性维持机制具有重要意义。

DNA-dependent protein kinase catalytic subunit (DNA-PKcs) plays a significant role in the process of non-homologous end-joining (NHEJ) repair，which is one of the major repair pathways for the IR-induced DSBs in mammalian cells. Cells that lack or have inactive DNA-PKcs have defects in repairing DSBs, disordered regulation of mitotic progress and increased radiosensitivity. Therefore, identifying the upstream and downstream regulators of DNA-PKcs and recognizing their functions have great significance in understand the genomic stability mechanism responding to IR-induced DNA damage. In our previous work, the salt-inducible kinase 2 (SIK2) was identified to interact with DNA-PKcs by the yeast two-hybridization. It was reported that SIK2 localizes at centrosomes, plays a key role in regulation of centrosomes separation and the onset of mitosis, via phosphorylating the centrosome linker protein,C-Nap1. Recently we also found DNA-PKcs play roles in regulating mitotic progression in IR-damaged cells, as well as stabilizing spindle and centrosome structures. In this study the cell cycle-dependent interaction between SIK2 and DNA-PKcs will be identified and the interaction domain of SIK2 with DNA-PKcs will be screened by GST pull-down assay. Besides the phosphorylation site(s) of SIK2 by DNA-PKcs will be determined by in vitro phosphorylation assay and in vivo. The effect of DNA-PKcs targeted phosphorylation of SIK2 on centrosome separation，spindle stability and mitotic progression will be further determined. Together with all these, The roles of the interaction between SIK2 and DNA-PKcs in G2/M arrest, spindle structure and mitotic progress will be ascertained, which will extend our knowledge in the molecular mechanism of cell radiosensitivity and genomic stability maintenance。