Foreman Hui-Chen Chang, Armstrong Julie, Santana Alexis L, Krug Laurie T, Reich Nancy C
From the Department of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook, New York 11794.
From the Department of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook, New York 11794
J Biol Chem. 2017 Sep 29;292(39):16257-16266. doi: 10.1074/jbc.M117.786970. Epub 2017 Aug 15.
Gammaherpesviruses (γHVs) have a dynamic strategy for lifelong persistence, involving productive infection, latency, and intermittent reactivation. In latency reservoirs, such as B lymphocytes, γHVs exist as viral episomes and express few viral genes. Although the ability of γHV to reactivate from latency and re-enter the lytic phase is challenging to investigate and control, it is known that the γHV replication and transcription activator (RTA) can promote lytic reactivation. In this study, we provide first evidence that RTA of murine γΗV68 (MHV68) selectively binds and enhances the activity of tyrosine-phosphorylated host STAT3. STAT3 is a transcription factor classically activated by specific tyrosine 705 phosphorylation (pTyr-STAT3) in response to cytokine stimulation. pTyr-STAT3 forms a dimer that avidly binds a consensus target site in the promoters of regulated genes, and our results indicate that RTA cooperatively enhances the ability of pTyr-STAT3 to induce expression of a STAT3-responsive reporter gene. As indicated by coimmunoprecipitation, in latently infected B cells that are stimulated to reactivate MHV68, RTA bound specifically to endogenous pTyr-STAT3. An binding assay confirmed that RTA selectively recognizes pTyr-STAT3 and indicated that the C-terminal transactivation domain of RTA was required for enhancing STAT3-directed gene expression. The cooperation of these transcription factors may influence both viral and host genes. During MHV68 infection, pTyr-STAT3 promoted the temporal expression of ORF59, a viral replication protein. Our results demonstrate that MHV68 RTA specifically recognizes and recruits activated pTyr-STAT3 during the lytic phase of infection.
γ疱疹病毒（γHVs）具有一种用于终身持续存在的动态策略，涉及增殖性感染、潜伏和间歇性再激活。在潜伏库中，如B淋巴细胞，γHVs以病毒附加体的形式存在，并且仅表达很少的病毒基因。尽管γHV从潜伏状态再激活并重新进入裂解期的能力难以研究和控制，但已知γHV复制和转录激活因子（RTA）可促进裂解性再激活。在本研究中，我们首次提供证据表明，小鼠γΗV68（MHV68）的RTA选择性结合并增强酪氨酸磷酸化的宿主STAT3的活性。STAT3是一种转录因子，通常在细胞因子刺激下通过特定的酪氨酸705磷酸化（pTyr-STAT3）而被激活。pTyr-STAT3形成二聚体，该二聚体强烈结合受调控基因启动子中的共有靶位点，并且我们的结果表明，RTA协同增强pTyr-STAT3诱导STAT3反应性报告基因表达的能力。如免疫共沉淀所示，在被刺激重新激活MHV68的潜伏感染B细胞中，RTA特异性结合内源性pTyr-STAT3。一项结合试验证实，RTA选择性识别pTyr-STAT3，并表明RTA的C末端反式激活结构域是增强STAT3指导的基因表达所必需的。这些转录因子的协同作用可能会影响病毒和宿主基因。在MHV68感染期间，pTyr-STAT3促进了病毒复制蛋白ORF59的瞬时表达。我们的结果表明，MHV68 RTA在感染的裂解期特异性识别并募集活化的pTyr-STAT3。
