Interferon alpha/beta (IFNalpha/Beta) mediate their antiviral, antiproliferative and immunemodulatory effects through the induction of a set of Interferon Stimulated early response Genes (ISGs). The STAT transcription factors have been identified as an important part of the IFNalpha/beta induced signaling cascade. STAT1 and STAT2 become tyrosine phosphorylated in response to IFNalpha/beta, an event that is mediated by the tyrosine kinases Jak1 and Tyk2. Subsequently, the STAT proteins translocate to the nucleus where they interact with several enhancer elements to induce transcription. The two aims of Part I are focused on characterizing the process of STAT1 nuclear translocation. During the current funding period we have shown that STAT1 is subject to nuclear export, which is regulated by Jak1 independent of tyrosine phosphorylation.
In Aim I we will investigate the mechanism by which Jak1 regulates STAT1 nuclear export. As no nuclear import signal has been identified in any of the STAT proteins thus far, we propose in Aim 2 experiments to identify and characterize the nuclear localization sequence of STAT1. Recently, we demonstrated that STAT 1 arginine methylation is required to prevent its interaction with the nuclear STAT-inhibitor PIAS1 and thus allow for DNA binding and transcription. We also identified additional modification of STAT1 and PIAS1 by ubiquitin-like molecules (SUMO) as a consequence of cytokine stimulation. Part II of the proposal contains two aims that investigate the role of STAT1 modification by ubiquitin and the ubiquitin-like molecule, SUMO-1.
In Aim 3 we will identify the sites of STAT1 and PIAS1 ubiquitination and SUMOylation, and determine the biological consequences of mutations in these sites.
In Aim 4 we will characterize the E3 ligase activity mediating STAT1 and PIAS1 ubiquitination/SUMOylation. In studying the immunemodulatory function of STAT1, we discovered that IFNbeta acts as a potent survival factor for primary, resting single positive T lymphocytes, but only in the absence of STAT1. The two aims of Part III focus on the elucidation of the anti-apoptotic effects of IFNalpha/beta in STAT 1 deficient primary T lymphocytes. Results from these proposed studies will not only improve our understanding of the mechanism of STAT activation, but will also shed light on the processes involved in the subcellular distribution of these signaling molecules. The investigation of the STAT1 independent mechanism by which IFNbeta prevents T cell apoptosis will elucidate additional IFNalpha/beta induced signaling pathways.

Agency
National Institute of Health (NIH)
Institute
National Cancer Institute (NCI)
Type
Research Project (R01)
Project #
3R01CA080105-04A1S1
Application #
6609821
Study Section
Medical Biochemistry Study Section (MEDB)
Program Officer
Rosenfeld, Bobby
Project Start
1999-06-29
Project End
2006-06-30
Budget Start
2002-08-01
Budget End
2003-06-30
Support Year
4
Fiscal Year
2002
Total Cost
$31,447
Indirect Cost
Name
University of California San Diego
Department
Biology
Type
Schools of Arts and Sciences
DUNS #
077758407
City
La Jolla
State
CA
Country
United States
Zip Code
92093
Hoyt, Richard; Zhu, Wei; Cerignoli, Fabio et al. (2007) Cutting edge: selective tyrosine dephosphorylation of interferon-activated nuclear STAT5 by the VHR phosphatase. J Immunol 179:3402-6
Otero, Dennis C; Poli, Valeria; David, Michael et al. (2006) Cutting edge: inherent and acquired resistance to radiation-induced apoptosis in B cells: a pivotal role for STAT3. J Immunol 177:6593-7
Tanabe, Yoshinari; Nishibori, Takeaki; Su, Leon et al. (2005) Cutting edge: role of STAT1, STAT3, and STAT5 in IFN-alpha beta responses in T lymphocytes. J Immunol 174:609-13
Smith, Wendell A; Schurter, Brandon T; Wong-Staal, Flossie et al. (2004) Arginine methylation of RNA helicase a determines its subcellular localization. J Biol Chem 279:22795-8
Nishibori, Takeaki; Tanabe, Yoshinari; Su, Leon et al. (2004) Impaired development of CD4+ CD25+ regulatory T cells in the absence of STAT1: increased susceptibility to autoimmune disease. J Exp Med 199:25-34
Ruvolo, Vivian; Navarro, Lorena; Sample, Clare E et al. (2003) The Epstein-Barr virus SM protein induces STAT1 and interferon-stimulated gene expression. J Virol 77:3690-701
ten Hoeve, Johanna; de Jesus Ibarra-Sanchez, Maria; Fu, Yubin et al. (2002) Identification of a nuclear Stat1 protein tyrosine phosphatase. Mol Cell Biol 22:5662-8
Zhu, Wei; Mustelin, Tomas; David, Michael (2002) Arginine methylation of STAT1 regulates its dephosphorylation by T cell protein tyrosine phosphatase. J Biol Chem 277:35787-90
Blesofsky, W A; Mowen, K; Arduini, R M et al. (2001) Regulation of STAT protein synthesis by c-Cbl. Oncogene 20:7326-33
Mowen, K A; Tang, J; Zhu, W et al. (2001) Arginine methylation of STAT1 modulates IFNalpha/beta-induced transcription. Cell 104:731-41

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