Regulation of STAT3 transcription activity by replication protein A 32 kDa

Abstract

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, I present evidence that the RPA p32 subunit specifically binds to the SH2 domain of STAT3 in a phosphotyrosine-independent manner. I 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. I 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.