去泛素化酶USP39通过Chk2调控DNA损伤应答及肺癌细胞凋亡的机制研究

Chk2 as the key protein in DNA damage response, regulates cell cycle turnover by activating downstream molecules, so that repair the damaged DNA and maintain the chromosome stability. The abnormal expression of Chk2 can affect DNA repair or DNA duplicating prevention and increase susceptibility to tumors. Based on this, Chk2 plays important role in tumorigenesis. There is a lack of expression in some lung cancer, but the molecular mechanism is not clear. Here we found Chk2 interact with USP39 and deubiquitinating by USP39, Chk2 protein expression decreased after knockdown USP39. Our project is intend to study if USP39 regulate DNA damage response and apoptosis of the lung cancer cells through Chk2 using Co-Immunoprecipitation, deubiquitination assay in vivo and in vitro, DNA damage response report system and apoptosis assay. Further we will analysis the correlation of protein expression between Chk2 and USP39 in lung cancer tissue. Then we will research on the USP39 regulation of lung cancer through Chk2 by using the cellular and nude mouse model, explore Chk2 and USP39 as a potential biomarker to provide a new theoretical basis for the molecular mechanism and clinical treatment of lung cancer.

Chk2作为DNA损伤修复中的关键蛋白，通过激活下游分子调节细胞周期的转换，使受损DNA得以修复并维持染色体稳定性。Chk2的表达异常会影响DNA损伤的修复或复制阻滞，增加了肿瘤的易感性。因此，Chk2在肿瘤发生中具有重要功能。Chk2在部分肺癌中存在表达缺失，但分子机制尚不明确。本项目前期研究发现，去泛素化酶USP39能够与Chk2互作，并且对Chk2有去泛素化作用；敲低USP39后，Chk2的蛋白表达水平降低。拟进一步通过免疫共沉淀，体内外去泛素化实验，DNA损伤应答检测报告系统，细胞凋亡检测等分子生物学手段，研究USP39能够通过Chk2调控DNA损伤应答及肺癌细胞凋亡，并分析肺癌组织中USP39与Chk2的蛋白表达及相关性，在细胞及动物模型上研究USP39是否通过Chk2调控肺癌的发生，探究USP39，Chk2作为生物标记物，为肺癌发生的分子机制及临床治疗提供新的理论依据。

丝氨酸/苏氨酸激酶CHK2是DNA损伤通路中的调节因子，也是一种重要的肿瘤抑制因子，通过磷酸化下游因子如p53和BRCA1，促进细胞周期阻滞、凋亡和DNA修复。目前尚不清楚去泛素化酶是否参与CHK2的调控。本项研究中，我们阐明了USP39对CHK2有去泛素化及稳定作用，shRNA介导的USP39基因敲低导致CHK2的表达下降，DNA损伤诱导的G2/M检查点受损，凋亡减少，并使癌细胞对放化疗产生耐药。在肺癌组织中USP39和CHK2低表达并且具有正相关性，肺癌患者USP39 的低表达与临床预后不良相关。综上所述，本项研究为探究肺癌发生机理，寻找肺癌临床治疗靶点提供了可靠的理论依据。

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