Implications of an antiparallel dimeric structure of nonphosphorylated STAT1 for the activation-inactivation cycle

Minghao Zhong, Melissa A. Henriksen, Kenji Takeuchi, Olaf Schaefer, Bin Liu, Johanna Ten Hoeve, Zhiyong Ren, Xiang Mao, Xiaomin Chen, Ke Shuai, James E. Darnell

Research output: Contribution to journalArticlepeer-review

127 Scopus citations

Abstract

IFN-γ treatment of cells leads to tyrosine phosphorylation of signal transducer and activator of transcription (STAT) 1 followed by dimerization through a reciprocal Src homology 2-phosphotyrosine interaction near the -COOH end of each monomer, forming a parallel structure that accumulates in the nucleus to drive transcription. Prompt dephosphorylation and return to the cytoplasm completes the activation-inactivation cycle. Nonphosphorylated STATs dimerize, and a previously described interface between N-terminal domain (ND) dimers has been implicated in this dimerization. A new crystal structure of nonphosphorylated STAT1 containing the ND dimer has two possible configurations for the body of STAT1, one of which is antiparallel. In this antiparallel structure, the Src homology 2 domains are at opposite ends of the dimer, with the coiled:coil domain of one monomer interacting reciprocally with the DNA-binding domain of its partner. Here, we find that mutations in either the coiled:coil/DNA-binding domain interface or the ND dimer interface block dimerization of nonphosphorylated molecules and cause a resistance to dephosphorylation in vivo and resistance to a tyrosine phosphatase in vitro. We conclude that a parallel STAT1 phosphodimer not bound to DNA most likely undergoes a conformational rearrangement (parallel to antiparallel) to present the phosphotyrosine efficiently for dephosphorylation.

Original languageEnglish (US)
Pages (from-to)3966-3971
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume102
Issue number11
DOIs
StatePublished - Mar 15 2005
Externally publishedYes

Keywords

  • Dephosphorylation
  • Rearrangement
  • Structural

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