title: Cytoplasmic STAT proteins associate prior to activation.
abstract: The commonly accepted model of STAT factor activation at the cytoplasmic part of the receptor assumes that signal transducers and activators of transcription (STATs) are recruited from a cytoplasmic pool of monomeric STAT proteins. Based on a previous observation that non-phosphorylated STAT3-Src homology 2 domains dimerize in vitro, we investigated whether the observed dimerization is of physiological relevance within the cellular context. We show that STAT1 and STAT3 are pre-associated in non-stimulated cells. Apparently, these complexes are not able to translocate into the nucleus. We provide evidence that the event of STAT activation is more complex than previously assumed.
authors.affiliation: Institut für Biochemie, Rheinisch-Westfälische Technische Hochschule Aachen, Pauwelsstrasse 30, D-52074 Aachen, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Haan
authors.forename: M
authors.initials: M
authors.lastname: Kortylewski
authors.forename: I
authors.initials: I
authors.lastname: Behrmann
authors.forename: W
authors.initials: W
authors.lastname: Müller-Esterl
authors.forename: P C
authors.initials: PC
authors.lastname: Heinrich
authors.forename: F
authors.initials: F
authors.lastname: Schaper
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D019556:COS Cells / Q000378:metabolism; D006528:Carcinoma, Hepatocellular / Q000188:drug therapy / Q000378:metabolism; D003429:Cross Reactions; D003593:Cytoplasm / Q000187:drug effects / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000187:drug effects / Q000276:immunology / Q000378:metabolism*; D019281:Dimerization; D006801:Humans; D015850:Interleukin-6 / Q000378:metabolism / Q000494:pharmacology; D008113:Liver Neoplasms / Q000188:drug therapy / Q000378:metabolism; D008545:Melanoma / Q000188:drug therapy / Q000378:metabolism; D008969:Molecular Sequence Data; D010766:Phosphorylation; D011233:Precipitin Tests; D050794:STAT1 Transcription Factor; D050796:STAT3 Transcription Factor; D015534:Trans-Activators / Q000187:drug effects / Q000276:immunology / Q000378:metabolism*; D014162:Transfection; D014407:Tumor Cells, Cultured; D014443:Tyrosine / Q000378:metabolism
chemical_list: D004268:DNA-Binding Proteins; D015850:Interleukin-6; D050794:STAT1 Transcription Factor; C494079:STAT1 protein, human; D050796:STAT3 Transcription Factor; C494086:STAT3 protein, human; D015534:Trans-Activators; D014443:Tyrosine