title: Distinct roles of the NH2- and COOH-terminal domains of the protein inhibitor of activated signal transducer and activator of transcription (STAT) 1 (PIAS1) in cytokine-induced PIAS1-Stat1 interaction.
abstract: STATs are activated by tyrosine phosphorylation on cytokine stimulation. A tyrosine-phosphorylated STAT forms a functional dimer through reciprocal Src homology 2 domain (SH2)-phosphotyrosyl peptide interactions. IFN treatment induces the association of PIAS1 and Stat1, which results in the inhibition of Stat1-mediated gene activation. The molecular basis of the cytokine-dependent PIAS1-Stat1 interaction has not been understood. We report here that a region near the COOH terminus of PIAS1 (amino acids 392-541) directly interacts with the NH(2)-terminal domain of Stat1 (amino acids 1-191). A mutant PIAS1 lacking the Stat1-interacting domain failed to inhibit Stat1-mediated gene activation. By using a modified yeast two-hybrid assay, we demonstrated that PIAS1 specifically interacts with the Stat1 dimer, but not tyrosine-phosphorylated or -unphosphorylated Stat1 monomer. In addition, whereas the NH(2)-terminal region of PIAS1 does not interact with Stat1, it serves as a modulatory domain by preventing the interaction of the COOH-terminal domain of PIAS1 with the Stat1 monomer. Thus, the cytokine-induced PIAS1-Stat1 interaction is mediated through the specific recognition of the dimeric form of Stat1 by PIAS1.
authors.affiliation: Division of Hematology-Oncology, Department of Medicine, University of California, Los Angeles, CA 90095, USA.
authors.forename: J
authors.initials: J
authors.lastname: Liao
authors.forename: Y
authors.initials: Y
authors.lastname: Fu
authors.forename: K
authors.initials: K
authors.lastname: Shuai
mesh_terms: D001665:Binding Sites; D002460:Cell Line; D003001:Cloning, Molecular; D016207:Cytokines / Q000494:pharmacology*; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000378:metabolism*; D019281:Dimerization; D004926:Escherichia coli; D005786:Gene Expression Regulation; D006801:Humans; D050828:Protein Inhibitors of Activated STAT; D011506:Proteins / Q000737:chemistry* / Q000378:metabolism*; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D050794:STAT1 Transcription Factor; D012441:Saccharomyces cerevisiae; D017384:Sequence Deletion; D015398:Signal Transduction; D015534:Trans-Activators / Q000737:chemistry* / Q000378:metabolism*; D015533:Transcriptional Activation; D014162:Transfection
chemical_list: D016207:Cytokines; D004268:DNA-Binding Proteins; D050828:Protein Inhibitors of Activated STAT; D011506:Proteins; D011994:Recombinant Proteins; D050794:STAT1 Transcription Factor; C494079:STAT1 protein, human; D015534:Trans-Activators