Tudor-SN蛋白调控细胞周期的分子机制研究

本课题组长期从事Tudor-SN蛋白结构与功能的系统研究，发现它由SN和Tudor两个功能片段组成。近期我们发现它在肿瘤细胞中高表达，相反在肌肉和粒细胞等终末期细胞中不表达。深入研究发现它可以促进G1/S进程；且其Thr-103位点可以被CDK1磷酸化。基于此我们提出本项目的设想：Tudor-SN参与调控细胞周期和细胞增殖，在细胞应激损伤下，参与DNA损伤修复，对细胞起保护作用。我们将利用HeLa细胞和独有的Tudor-SN基因敲除MEF细胞，通过周期同步化、流式测定、甘油密度梯度离心、免疫共沉淀等方法探讨Tudor-SN是否被CDK2/CDK4/CDK6等磷酸化，调控E2F1/Rb的结合促进G1/S期进程；是否作为CDK1底物，Thr-103位点特异性磷酸化后，调控G2-M期进程；在UV诱导损伤下，p53激活CDK1过度磷酸化，是否促进Tudor-SN磷酸化，参与DNA损伤修复。

Cell cycle changes according to the extra-cellular environment, cyclins and cycle control related regulation of protein consisting of protein interaction networks. Tudor-SN is a multifunctional protein, our previous study indicated that decreased expression of Tudor-SN caused G1/G0 arrest, while overexpression promoted the G1/S process; and mass spectrometry analysis found that CDK1 could phosphorylate Thr-103 site of Tudor-SN. We thus hypothesize that Tudor-SN is a novel regulator involved in regulating cell cycle and proliferation, and may also be involved in DNA damage repair caused by cellular stress damage signals. In this present study, we will use the original Tudor-SN gene knockout MEF model to explore the Tudor-SN molecular mechanism of the regulation of cell cycle: missing Tudor-SN protein causes G1 phase arrest, as well as why the end-stage (G0) cells do not express Tudor-SN protein; as Tudor-SN is the substrate of CDK1, Tudor-SN protein　may exist in the same protein complex with CDK1/cyclinB1 to regulate and process the G2-M stage; on the other hand, Tudor-SN protein may also be involved in DNA damage repair, as p53 could enhance the CDK1 activity under DNA damage signal. From the perspective of cell cycle regulation on noval functionality to Tudor-SN, it may highlight molecular mechanism of high level expression of Tudor-SN in breast cancer, colon cancer, prostate cancer and other tumor.