title: The STAT3 NH2-terminal domain stabilizes enhanceosome assembly by interacting with the p300 bromodomain.
abstract: Signal transducer and activator of transcription 3 (STAT3) is a latent transcription factor mainly activated by the interleukin-6 cytokine family. Previous studies have shown that activated STAT3 recruits p300, a coactivator whose intrinsic histone acetyltransferase activity is essential for transcription. Here we investigated the function of the STAT3 NH(2)-terminal domain and how its interaction with p300 regulates STAT3 signal transduction. In STAT3(-/-) mouse embryonic fibroblasts, a stably expressed NH(2) terminus-deficient STAT3 mutant (STAT3-DeltaN) was unable to efficiently induce either STAT3-mediated reporter activity or endogenous mRNA expression. Chromatin immunoprecipitation assays were performed to determine whether the NH(2)-terminal domain regulates p300 recruitment or stabilizes enhanceosome assembly. Despite equivalent levels of STAT3 binding, cells expressing the STAT3-DeltaN mutant were unable to recruit p300 and RNA polymerase II to the native socs3 promoter as efficiently as those expressing STAT3-full length. We previously reported that the STAT3 NH(2)-terminal domain is acetylated by p300 at Lys-49 and Lys-87. By introducing K49R/K87R mutations, here we found that the acetylation status of the STAT3 NH(2)-terminal domain regulates its interaction with p300. In addition, the STAT3 NH(2)-terminal binding site maps to the p300 bromodomain, a region spanning from amino acids 995 to 1255. Finally a p300 mutant lacking the bromodomain (p300-DeltaB) exhibited a weaker binding to STAT3, and the enhanceosome formation on the socs3 promoter was inhibited when p300-DeltaB was overexpressed. Taken together, our data suggest that the STAT3 NH(2)-terminal domain plays an important role in the interleukin-6 signaling pathway by interacting with the p300 bromodomain, thereby stabilizing enhanceosome assembly.
authors.affiliation: Department of Biochemistry, University of Texas Medical Branch, Galveston, Texas 77555-1060, USA.
authors.forename: Tieying
authors.initials: T
authors.lastname: Hou
authors.forename: Sutapa
authors.initials: S
authors.lastname: Ray
authors.forename: Chang
authors.initials: C
authors.lastname: Lee
authors.forename: Allan R
authors.initials: AR
authors.lastname: Brasier
mesh_terms: D019943:Amino Acid Substitution; D000818:Animals; D045744:Cell Line, Tumor; D004622:Embryo, Mammalian / Q000166:cytology / Q000378:metabolism; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism; D051548:Histone Acetyltransferases / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D015850:Interleukin-6 / Q000235:genetics / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D020125:Mutation, Missense; D011485:Protein Binding / Q000502:physiology; D017434:Protein Structure, Tertiary / Q000502:physiology; D012319:RNA Polymerase II / Q000235:genetics / Q000378:metabolism; D050796:STAT3 Transcription Factor / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology*; D014158:Transcription, Genetic / Q000502:physiology*; D050880:p300-CBP Transcription Factors / Q000235:genetics / Q000378:metabolism*
chemical_list: C508600:IL6 protein, human; D015850:Interleukin-6; D050796:STAT3 Transcription Factor; C494086:STAT3 protein, human; C494087:Stat3 protein, mouse; D051548:Histone Acetyltransferases; D050880:p300-CBP Transcription Factors; D012319:RNA Polymerase II
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