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Functional inactivation of a transcriptional corepressor by a signaling kinase

Christopher J Barnes1, Ratna K Vadlamudi, Sandip K Mishra

  • 1Department of Molecular and Cellular Oncology, The University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030, USA.

Nature Structural Biology
|July 23, 2003
PubMed

Insights

The p21-activated kinase 1 (Pak1) regulates the C-terminal binding protein 1 (CtBP) through phosphorylation. This phosphorylation affects CtBP

Area of Science:

  • Molecular Biology
  • Gene Regulation
  • Signal Transduction

Background:

  • C-terminal binding protein 1 (CtBP) is a key corepressor involved in gene regulation during development and cancer.
  • CtBP links DNA-binding proteins with chromatin-modifying enzymes, influencing gene expression.
  • Understanding CtBP regulation is crucial for deciphering cellular signaling pathways.

Purpose of the Study:

  • To investigate the interaction and functional regulation of CtBP by p21-activated kinase 1 (Pak1).
  • To elucidate the mechanism by which Pak1 modulates CtBP's corepressor and enzymatic activities.
  • To establish a novel regulatory pathway for gene expression control in mammalian cells.

Main Methods:

  • Site-directed mutagenesis to create CtBP S158A substitution.
  • Short interference RNA (siRNA) for Pak1 knockdown.
  • Cellular redistribution assays, reporter assays, and chromatin assays.
  • Enzymatic assays to measure CtBP dehydrogenase activity.

Main Results:

  • Pak1 selectively phosphorylates CtBP at Ser158, causing its redistribution and inhibiting its corepressor function.
  • CtBP S158A mutation or Pak1 knockdown prevents phosphorylation, redistribution, and loss of CtBP function.
  • Pak1 superphosphorylates CtBP in the presence of NADH, inhibiting its dehydrogenase activity.

Conclusions:

  • Pak1 acts as a novel regulator of CtBP, impacting both its enzymatic and corepressor functions.
  • Phosphorylation of CtBP by Pak1 provides a mechanism for cellular signaling to influence gene expression.
  • This study reveals a new model for corepressor regulation via kinase signaling cascades.

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