title: Functional interaction of STAT5 and nuclear receptor co-repressor SMRT: implications in negative regulation of STAT5-dependent transcription.
abstract: Signal transducers and activators of transcription (STATs) play a central role in cytokine signaling. Activating and repressing gene transcription is a dynamic process involving chromatin remodeling by histone acetylases and deacetylases, yet the role of this process in STAT-dependent transcription remains largely unknown. In a search for STAT5-interacting proteins by yeast two-hybrid screening, we identified the nuclear receptor co-repressor SMRT (silencing mediator for retinoic acid receptor and thyroid hormone receptor) as a potential STAT5-binding partner. SMRT binds to both STAT5A and 5B, and strongly repressed STAT5-dependent transcription in vitro. SMRT binds to the N-terminal coiled-coil domain of STAT5 and a mutation within this region previously found to render STAT5 hyperactive in response to cytokines abolished the interaction with SMRT. Overexpression of SMRT suppressed the induction of STAT5 target genes by interleukin-3, whereas the histone deacetylase inhibitor trichostatin A effectively enhanced and prolonged their expression. Together, these findings illuminate the potential role of SMRT in down-regulating STAT5 activity, with a consequent reduction of STAT5 target gene expression.
authors.affiliation: Department of Biochemistry, St Jude Children's Research Hospital, Memphis, TN 38105, USA. hnakajim@ims.u-tokyo.ac.jp
authors.forename: H
authors.initials: H
authors.lastname: Nakajima
authors.forename: P K
authors.initials: PK
authors.lastname: Brindle
authors.forename: M
authors.initials: M
authors.lastname: Handa
authors.forename: J N
authors.initials: JN
authors.lastname: Ihle
mesh_terms: D015152:Blotting, Northern; D015153:Blotting, Western; D002460:Cell Line; D016207:Cytokines / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism*; D015536:Down-Regulation; D004591:Electrophoresis, Polyacrylamide Gel; D005786:Gene Expression Regulation; D006801:Humans; D007377:Interleukin-3 / Q000378:metabolism; D008156:Luciferases / Q000378:metabolism; D008894:Milk Proteins; D009154:Mutation; D056985:Nuclear Receptor Co-Repressor 2; D010957:Plasmids / Q000378:metabolism; D017354:Point Mutation; D011233:Precipitin Tests; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D012097:Repressor Proteins / Q000235:genetics* / Q000378:metabolism*; D050799:STAT5 Transcription Factor; D015398:Signal Transduction; D015534:Trans-Activators / Q000235:genetics* / Q000378:metabolism*; D014158:Transcription, Genetic; D014162:Transfection; D025521:Tumor Suppressor Proteins; D020798:Two-Hybrid System Techniques
chemical_list: D016207:Cytokines; D004268:DNA-Binding Proteins; D007377:Interleukin-3; D008894:Milk Proteins; C539130:NCOR2 protein, human; D056985:Nuclear Receptor Co-Repressor 2; D012097:Repressor Proteins; D050799:STAT5 Transcription Factor; C494092:STAT5A protein, human; C494095:STAT5B protein, human; D015534:Trans-Activators; D025521:Tumor Suppressor Proteins; D008156:Luciferases