Look D C, Pelletier M R, Tidwell R M, Roswit W T, Holtzman M J
Department of Medicine, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
J Biol Chem. 1995 Dec 22;270(51):30264-7. doi: 10.1074/jbc.270.51.30264.
STAT (signal transducer and activator of transcription) proteins combine with cytokine receptors and receptor-associated kinases in distinct protein/protein interactions that are critical for STAT-dependent signal transduction events, but the nature of any subsequent STAT interactions with DNA-binding proteins in the nucleus is less certain. Based on assays of DNA/protein binding and activity of transfected reporter plasmids, we determined that occupation of contiguous DNA-binding sites for Stat1 (the first member of the STAT family) and the transcriptional activator Sp1 are both required for full activation of the intercellular adhesion molecule-1 gene by interferon-gamma. Thus, Stat1 binding to DNA cannot by itself be equated with biologic actions of Stat1. In co-immunoprecipitation experiments, we also obtained evidence of direct and selective Stat1/Sp1 interaction (in primary culture cells without overexpression), further indicating that Stat1/Sp1 synergy confers an element of specificity in the pathway leading to cytokine-activated transcription and cytokine-dependent immunity and inflammation.
信号转导与转录激活因子（STAT）蛋白通过独特的蛋白质/蛋白质相互作用与细胞因子受体及受体相关激酶结合，这些相互作用对于依赖STAT的信号转导事件至关重要，但随后STAT在细胞核中与DNA结合蛋白相互作用的性质尚不太明确。基于DNA/蛋白质结合分析和转染报告质粒的活性测定，我们确定Stat1（STAT家族的首个成员）连续的DNA结合位点以及转录激活因子Sp1的占据对于干扰素-γ完全激活细胞间黏附分子-1基因都是必需的。因此，Stat1与DNA的结合本身不能等同于Stat1的生物学作用。在共免疫沉淀实验中，我们还获得了直接和选择性的Stat1/Sp1相互作用的证据（在未过表达的原代培养细胞中），进一步表明Stat1/Sp1协同作用在导致细胞因子激活转录以及细胞因子依赖性免疫和炎症的途径中赋予了特异性元素。
