The Role of Arginine Methyltransferases in Interferon Signaling

描述(申请人提供)：细胞因子干扰素(干扰素)(/(通过参与JAK/STAT信号通路介导其抗病毒、抗增殖和免疫调节作用。连接干扰素(/)受体导致Jak酪氨酸激酶的激活和随后STAT1的酪氨酸磷酸化。磷酸化的STAT1通过SH2结构域的相互作用与STAT2形成同源二聚体或异源二聚体。然后，二聚化的STATs转移到细胞核，在那里它们与干扰素反应基因中的调节元件结合。除了酪氨酸激酶，精氨酸甲基转移酶(PRMT)还通过与JAK/STAT通路成员的物理联系和遗传学研究参与了干扰素(/)信号通路。丙型肝炎病毒通过靶向STAT1的精氨酸甲基化来干扰干扰素信号转导。我们现在已经发现，Carm1精氨酸甲基转移酶缺陷的细胞对干扰素驱动的STAT1激活的反应增强，包括STAT1去磷酸化和。此外，在体外实验中，Carm1可以使STAT1甲基化。我们的假设是，Carm1通过促进TCPTP对STAT1的去磷酸化来负向调节STAT1介导的转录。具体目标：1)确定Carm1在IFN1/2信号通路中的交叉点。我们将研究STAT1的DNA结合、四聚化以及与靶基因的关联。我们还将描述JAK1、TYK2、STAT1、STAT2、STAT3和STAT5的活性。2)确定Carm1调节STAT1去磷酸化的机制，包括研究Carm1催化活性的重要性以及Carm1对STAT1与Pias1和TCPTP相互作用的影响。将确定STAT1甲基化位点。3)研究Carm1受干扰素(/)信号通路的调控，包括表达、酶活性、亚细胞定位和翻译后修饰。意义重大。这些研究将深入了解PRMT调节I型干扰素信号的机制，该信号在病毒感染期间可能会改变。与公共卫生相关：干扰素家族的细胞因子通过调节细胞增殖和抗病毒防御以及通过直接调节免疫反应来控制病原体感染。出于这些原因，干扰素被用于临床治疗病毒性疾病和恶性疾病。我们的项目将解决干扰素信号被衰减的分子机制。

DESCRIPTION (provided by applicant): The cytokine Interferon (IFN) (/( mediates its antiviral, antiproliferative, and immunomodulatory effects through the engagement of the Jak/Stat signaling pathway. Ligation of the IFN(/( receptor results in activation of Jak tyrosine kinases and subsequent tyrosine phosphorylation of Stat1. Phosphorylated Stat1 either forms homodimers or heterodimerizes with Stat2 via reciprocal SH2 domain interactions. Dimerized Stats then translocate to the nucleus where they bind to regulatory elements in IFN response genes. In addition to tyrosine kinases, protein arginine methyltransferases (PRMT) have been implicated in IFN(/( signaling pathways through their physical association with members of the Jak/Stat pathway and through genetic studies. The Hepatitis C Virus interferes with IFN signaling by targeting arginine methylation of Stat1. We have now found that cells deficient in the Carm1 arginine methyltransferase exhibited elevated responses to IFN(-driven Stat1 activation, including a deficiency in Stat1 dephosphorylation and. Furthermore, Carm1 can methylate Stat1 in in vitro assays. Our HYPOTHESIS is that Carm1 negatively regulates Stat1 driven transcription by promoting the dephosphorylation of Stat1 by TCPTP. Specific Aims: 1) Define the intersection of Carm1 within IFN1/2 signaling pathways. We will examine Stat1 DNA binding, tetramerization, and association with target genes. We will also characterize the activity of Jak1, Tyk2, Stat1, Stat2, Stat3, and Stat5. 2) Determine the mechanism by which Carm1 regulates Stat1 dephosphorylation, including examining the importance of Carm1 catalytic activity and the effects on Carm1 on Stat1 interaction with Pias1 and TCPTP. The Stat1 methylation site will be determined. 3) Investigate the regulation of Carm1 by the IFN(/( signaling pathway, including expression, enzymatic activity, subcellular localization, and posttranslational modifications. Significance. These studies will provide insight into the mechanisms by which PRMTs regulate Type I IFN signaling, which may be altered during viral infection. PUBLIC HEALTH RELEVANCE: The interferon family of cytokines control pathogen infections through regulation of cellular proliferation and antiviral defenses, as well as through direct modulation of the immune response. For these reasons, the interferons are used clinically to treat viral and malignant diseases. Our project will address the molecular mechanisms of by which interferon signals are attenuated.