BIOCHEMICAL STUDIES OF STAT NUCLEAR LOCALIZATION

描述(由申请人提供)： 该研究计划的广泛和长期目标是揭示JAK/STAT介导的信号转导和转录激活的分子机制。STATs之所以这样命名，是因为它们是细胞质中的信号转导分子和细胞核中的转录激活器。当配体结合诱导受体二聚体时，JAK或受体酪氨酸激酶被激活，进而使受体上的酪氨酸磷酸化。含有SH2的STAT分子被募集到细胞表面，并被JAK或受体激酶磷酸化。随后，它们同源或异源二聚体并移位到细胞核中，在那里它们与特定的DNA靶标结合，并直接启动特定的转录。Jak/STAT通路参与了几乎所有细胞因子和生长因子的信号传递过程。这一途径的失调导致STAT蛋白的结构性激活，以及随后凋亡抑制物和细胞周期调节因子基因的上调。结构性激活的STATs与许多癌症细胞系和实体肿瘤有关，包括白血病和乳腺癌。因此，它们已成为抗癌药物发现的重要靶点。这项研究的主要焦点是阐明原子分辨率下STAT原子核局域化的分子机制。拟议研究的具体目标包括：(1)确定非磷酸化全长STAT的晶体结构；(2)利用生化、生物物理和细胞生物学工具研究观察到的非磷酸化STAT二聚体结构的生理意义；以及(3)利用生化、结构和细胞生物学工具研究STAT1：NPI1相互作用及其在STAT1核定位中的作用。

DESCRIPTION (provided by applicant): The broad and long-term objectives of the research program are to uncover the molecular mechanism of Jak/STAT-mediated signal transduction and transcription activation. STATs are so named since they are signal transducers in the cytoplasm and activators of transcription in the nucleus. Upon receptor dimerization induced by ligand binding, Jak or receptor tyrosine kinases are activated and they in turn phosphorylate tyrosines on the receptors. The SH2-containing STAT molecules are recruited to the cell surface and become tyrosine phosphorylated by Jak or receptor kinases. They subsequently homo- or hetero-dimerize and translocate into the nucleus, where they bind to specific DNA targets and direct specific transcription initiation. The Jak/STAT pathway is involved in the signaling process of virtually every cytokine and growth factor. Dysregulation of this pathway leads to constitutively activated STAT proteins and the subsequent up-regulation of the genes of apoptosis inhibitors and cell cycle regulators. Constitutively activated STATs have been linked to numerous cancer cell lines and solid tumors including leukemia and breast cancer. Thus they have become important targets for cancer drug discovery. The major focus of this research is to elucidate the molecular mechanism underlying STAT nuclear localization at atomic resolution. The specific aims of the proposed research include (1) to determine the crystal structure of an unphosphorylated full-length STAT; (2) to study the physiological significance of the observed unphosphorylated STAT dimer structure using biochemical, biophysical, and cell biological tools; and (3) to study STAT1:NPI1 interaction and its role in STAT1 nuclear localization using biochemical, structural, and cell biological tools.