Cytoplasmic STAT proteins associate prior to activation.
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.
Haan
S
S
Institut für Biochemie, Rheinisch-Westfälische Technische Hochschule Aachen, Pauwelsstrasse 30, D-52074 Aachen, Germany.
Kortylewski
M
M
Behrmann
I
I
Müller-Esterl
W
W
Heinrich
P C
PC
Schaper
F
F
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
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