Arginine/lysine-rich structural element is involved in interferon-induced nuclear import of STATs
Arginine/lysine-rich structural element is involved in interferon-induced nuclear import of STATs
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DOI：
10.1074/jbc.m008821200
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发表时间：
2001-05-11
影响因子：
4.8
通讯作者：
Julkunen, I
中科院分区：
文献类型：
--
作者：
Melén, K;Kinnunen, L;Julkunen, I
信号转导和转录激活因子（signaltransducersandactivatorsoftranscription，STAT）是一种潜在的细胞质转录因子，介导干扰素（interferon，IFN）、白细胞介素（interleukin，IL）以及一些生长因子和肽类激素的信号转导，IFN刺激后STATs发生酪氨酸磷酸化、二聚化和核内转运。响应于IFN-γ刺激，STAT 1形成同源二聚体，而IFN-α诱导导致STAT 1、STAT 2异源二聚体的形成，其在细胞核中与p48蛋白组装。磷酸化本身不足以将STAT靶向到细胞核中;相反，由磷酸化触发的二聚化是必需的。虽然IFN诱导的STAT核输入是通过输入素/Ran转运系统介导的，但在STAT中没有发现经典的核定位信号（NLS）。在STAT 1的三维结构中，我们观察到该分子的DNA结合结构域内的结构精氨酸/赖氨酸丰富的元素。我们在STAT 1和STAT 2的这些元件中创建了一系列点突变，并通过瞬时转染/IFN刺激试验表明，该位点对于STAT 1和STAT 2的核输入至关重要。结果表明，IFN诱导的STAT二聚体的核输入需要两个富含精氨酸/赖氨酸的元件，每个STAT单体中一个，输入缺陷的STAT 1和STAT 2蛋白容易磷酸化和二聚化，但它们作为显性负性分子抑制异源STAT蛋白的核输入。
Signal transducers and activators of transcription (STATs) are latent cytoplasmic transcription factors, which mediate interferon (IFN), interleukin, and some growth factor and peptide hormone signaling in cells, IFN stimulation results in tyrosine phosphorylation, dimerization, and nuclear import of STATs. In response to IFN-gamma stimulation, STAT1 forms homodimers, whereas IFN-alpha induction results in the formation of STAT1.STAT2 heterodimers, which assemble with p48 protein in the nucleus. Phosphorylation as such is not sufficient to target STATs into the nucleus; rather, the dimerization triggered by phosphorylation is essential. Although IFN-induced nuclear import of STATs is mediated by the importin/Ran transport system, no classic nuclear localization signal (NLS) has been found in STATs. In the three-dimensional structure of STAT1, we observed a structural arginine/lysine-rich element within the DNA-binding domain of the molecule. We created a series of point mutations in these elements of STAT1 and STAT2 and showed by transient transfection/IFN stimulation assay that this site is essential for the nuclear import of both STAT1 and STAT2. The results suggest that two arginine/lysine-rich elements, one in each STAT monomer, are required for IFN-induced nuclear import of STAT dimers, import-defective STAT1 and STAT2 proteins were readily phosphorylated and dimerized, but they functioned as dominant negative molecules inhibiting the nuclear import of heterologous STAT protein.