Kim J, Kim D, Chung J
Department of Biological Sciences, Korea Advanced Institute of Science and Technology, Kusong-dong, Yusong, Taejon, 305-701, Korea.
Cell Biol Int. 2000;24(7):467-73. doi: 10.1006/cbir.2000.0525.
STATs (signal transducers and activators of transcription) are transcription factors that contain SH2 domains and are activated by tyrosine phosphorylation in response to cytokines and growth factors. Replication protein A (RPA) is a heterotrimeric complex that consists of three subunits, p70, p32 and p11, and has important functions in DNA replication and metabolism. Here, we present evidence that the RPA p32 subunit binds specifically to the SH2 domain of STAT3 in a phosphotyrosine-independent manner. We confirm their protein-protein interactions by yeast 2-hybrid analyses and in vitro binding assays using recombinant proteins generated from bacteria and in vitro translation. We also show that STAT3 binds to RPA p32 in vivo by conducting co-precipitation experiments. As the SH2 domain is highly involved in the tyrosine phosphorylation and the transcriptional activity of STAT3, over-expression of RPA p32 correspondingly augmented growth factor-stimulated tyrosine phosphorylation and transcription activities of STAT3.
信号转导子与转录激活子（STATs）是一类转录因子，含有SH2结构域，可响应细胞因子和生长因子通过酪氨酸磷酸化被激活。复制蛋白A（RPA）是一种异源三聚体复合物，由三个亚基p70、p32和p11组成，在DNA复制和代谢中具有重要功能。在此，我们提供证据表明，RPA的p32亚基以不依赖磷酸酪氨酸的方式与STAT3的SH2结构域特异性结合。我们通过酵母双杂交分析以及使用细菌产生的重组蛋白和体外翻译进行的体外结合试验，证实了它们的蛋白质-蛋白质相互作用。我们还通过共沉淀实验表明STAT3在体内与RPA p32结合。由于SH2结构域高度参与STAT3的酪氨酸磷酸化和转录活性，RPA p32的过表达相应增强了生长因子刺激的STAT3的酪氨酸磷酸化和转录活性。
