Li Jing, Diaz Jason, Wang Xin, Tsang Sabrina H, You Jianxin
From the The Wistar Institute, Philadelphia, Pennsylvania 19104.
the Department of Microbiology, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania 19104, and.
J Biol Chem. 2015 Jan 16;290(3):1874-84. doi: 10.1074/jbc.M114.594895. Epub 2014 Dec 5.
Merkel cell carcinoma is a highly aggressive form of skin cancer. Merkel cell polyomavirus (MCV) infection and DNA integration into the host genome correlate with 80% of all Merkel cell carcinoma cases. Integration of the MCV genome frequently results in mutations in the large tumor antigen (LT), leading to expression of a truncated LT that retains pRB binding but with a deletion of the C-terminal domain. Studies from our laboratory and others have shown that the MCV LT C-terminal helicase domain contains growth-inhibiting properties. Additionally, we have shown that host DNA damage response factors are recruited to viral replication centers. In this study, we identified a novel MCV LT phosphorylation site at Ser-816 in the C-terminal domain. We demonstrate that activation of the ATM pathway stimulated MCV LT phosphorylation at Ser-816, whereas inhibition of ATM kinase activity prevented LT phosphorylation at this site. In vitro phosphorylation experiments confirmed that ATM kinase is responsible for phosphorylating MCV LT at Ser-816. Finally, we show that ATM kinase-mediated MCV LT Ser-816 phosphorylation may contribute to the anti-tumorigenic properties of the MCV LT C-terminal domain.
默克尔细胞癌是一种侵袭性很强的皮肤癌。默克尔细胞多瘤病毒（MCV）感染以及DNA整合到宿主基因组与所有默克尔细胞癌病例中的80%相关。MCV基因组的整合经常导致大肿瘤抗原（LT）发生突变，从而导致截短的LT表达，该截短的LT保留了与pRB的结合，但C末端结构域缺失。我们实验室及其他机构的研究表明，MCV LT C末端解旋酶结构域具有生长抑制特性。此外，我们还表明宿主DNA损伤反应因子被招募到病毒复制中心。在本研究中，我们在C末端结构域的Ser-816处鉴定出一个新的MCV LT磷酸化位点。我们证明，ATM途径的激活刺激了Ser-816处的MCV LT磷酸化，而抑制ATM激酶活性则阻止了该位点的LT磷酸化。体外磷酸化实验证实，ATM激酶负责在Ser-816处磷酸化MCV LT。最后，我们表明ATM激酶介导的MCV LT Ser-816磷酸化可能有助于MCV LT C末端结构域的抗肿瘤特性。
