Transcription factor ISGF-3 formation requires phosphorylated Stat91 protein, but Stat113 protein is phosphorylated independently of Stat91 protein

Teresa Improta, Chris Schindler, Curt M. Horvath, Ian M. Kerr, G. R. Stark, J. E. Darnell*

*Corresponding author for this work

Research output: Contribution to journalArticle

120 Scopus citations


Transcription factor ISGF-3 is a multiprotein, interferon α-activated transcription complex consisting of a 48-kDa DNA-binding protein and two proteins termed Stats (for signal transducers and activators of transcription) that become phosphorylated on tyrosine in the cell cytoplasm, a 113-kDa and either a 91- or 84-kDa polypeptide, the latter two of which arise from differentially spliced mRNAs. Using cell lines lacking the Stat91 or Stat84 proteins, we show that mutations in several different sites in the 91-kDa protein block the interferon α-induced phosphorylation of the 91-kDa protein and subsequent ISGF-3 formation. Although correct tyrosine phosphorylation on residue 690 of the Stat113 protein occurs independent of the Stat91/84 protein, the Stat113 phosphoprotein by itself moves to the cell nucleus much less efficiently in the absence of phosphorylated Stat91/84 protein.

Original languageEnglish (US)
Pages (from-to)4776-4780
Number of pages5
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number11
StatePublished - May 24 1994



  • interferon
  • transcription
  • tyrosine phosphorylation

ASJC Scopus subject areas

  • General

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