The Role of Arginine Methyltransferases in Interferon Signaling

描述（由申请人提供）：细胞因子干扰素（IFN）α通过参与Jak/Stat信号传导途径介导其抗病毒、抗增殖和免疫调节作用。IFN α受体的连接导致Jak酪氨酸激酶的活化和随后的Stat 1的酪氨酸磷酸化。磷酸化的Stat 1通过相互的SH 2结构域相互作用与Stat 2形成同源二聚体或异源二聚体。二聚化的Stats然后转移到细胞核，在那里它们与IFN应答基因中的调节元件结合。除酪氨酸激酶外，蛋白质精氨酸甲基转移酶（PRMT）通过与Jak/Stat途径成员的物理关联和通过遗传研究而与IFN α信号传导途径有关。丙型肝炎病毒通过靶向Stat 1的精氨酸甲基化干扰IFN信号传导。我们现在已经发现，缺乏Carm 1精氨酸甲基转移酶的细胞对IFN β驱动的Stat 1活化表现出更高的反应，包括Stat 1去磷酸化的缺陷和。此外，Carm 1可以在体外测定中甲基化Stat 1。我们的假设是Carm 1通过促进TCPTP对Stat 1的去磷酸化而负调控Stat 1驱动的转录。具体目的：1）确定Carm 1在IFN 1/2信号通路中的交叉点。我们将研究Stat 1 DNA结合，四聚体，并与靶基因的关联。我们还将表征Jak 1、Tyk 2、Stat 1、Stat 2、Stat 3和Stat 5的活性。2)确定Carm 1调节Stat 1去磷酸化的机制，包括检查Carm 1催化活性的重要性以及Carm 1对Stat 1与Pias 1和TCPTP相互作用的影响。将确定Stat 1甲基化位点。3)研究Carm 1通过IFN（/）信号通路的调节，包括表达、酶活性、亚细胞定位和翻译后修饰。意义这些研究将提供深入了解PRMT调节I型IFN信号传导的机制，该机制可能在病毒感染期间改变。公共卫生相关性：细胞因子的干扰素家族通过调节细胞增殖和抗病毒防御以及通过直接调节免疫应答来控制病原体感染。由于这些原因，干扰素在临床上用于治疗病毒性和恶性疾病。我们的项目将解决干扰素信号减弱的分子机制。

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.