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Region 752-761 of STAT3 is critical for SRC-1 recruitment and Ser727 phosphorylation

Hong Zhao1, Ryota Nakajima, Hiroyuki Kunimoto

  • 1Department of Immunology, Osaka City University Graduate School of Medicine, 1-4-3 Asahi-machi, Abeno-ku, Osaka 545-8585, Japan.

Biochemical and Biophysical Research Communications
|November 9, 2004
PubMed

Insights

The STAT3 CR2 region (amino acids 752-761) is crucial for STAT3-dependent gene transcription. It facilitates SRC-1 recruitment and Ser727 phosphorylation, impacting histone modifications and RNA polymerase II binding.

Area of Science:

  • Molecular Biology
  • Gene Regulation
  • Signal Transduction

Background:

  • Signal transducer and activator of transcription 3 (STAT3) is a key transcription factor involved in cellular responses to cytokines and growth factors.
  • Understanding the precise mechanisms of STAT3-mediated gene regulation is essential for deciphering complex biological processes.

Purpose of the Study:

  • To investigate the functional role of specific STAT3 domains in STAT3-dependent transcription.
  • To elucidate the molecular mechanisms by which STAT3 interacts with coactivators and regulates target gene promoters.

Main Methods:

  • Generation of HepG2 cell lines with STAT3 knockdown, reconstituted with various STAT3 mutants.
  • Assessment of STAT3 mutant recruitment of SRC-1/NcoA-1.
  • Analysis of STAT3 phosphorylation at Ser727.
  • ChIP assays to measure histone modifications (acetylation) and RNA polymerase II recruitment to target gene promoters.

Main Results:

  • Truncated STAT3(1-750) failed to recruit SRC-1/NcoA-1 and was not phosphorylated at Ser727.
  • Mutations at STAT3 L755 and F757 abolished STAT3-dependent SRC-1 recruitment but preserved Ser727 phosphorylation.
  • The STAT3-L755A/F757A mutant exhibited reduced histone H3 acetylation and RNA polymerase II recruitment, despite intact p300 recruitment and histone H4 acetylation.
  • This mutant also showed diminished responsiveness to SRC-1 co-expression.

Conclusions:

  • The STAT3 CR2 region (amino acids 752-761) is critical for STAT3-dependent transcription.
  • This region mediates the recruitment of the coactivator SRC-1, which is essential for Ser727 phosphorylation and subsequent transcriptional activation.
  • STAT3 CR2 plays a vital role in regulating target gene expression through interactions with coactivators and chromatin-modifying enzymes.

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