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Identification of Cyclin-dependent Kinase 1 Specific Phosphorylation Sites by an In Vitro Kinase Assay
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CDK9 phosphorylates p53 on serine residues 33, 315 and 392

Senthil K Radhakrishnan1, Andrei L Gartel

  • 1Department of Medicine, University of Illinois at Chicago, Chicago, Illinois 60612, USA.

Cell Cycle (Georgetown, Tex.)
|March 23, 2006
PubMed

Insights

The tumor suppressor p53 protein is phosphorylated by Cyclin dependent kinase 9 (CDK9) at specific sites. This newly identified interaction may influence p53

Area of Science:

  • Molecular Biology
  • Cellular Stress Response
  • Protein Kinase Signaling

Background:

  • Tumor suppressor p53 is crucial for cellular stress response, mediating cell cycle arrest or apoptosis.
  • p53 stability and activity are regulated by phosphorylation by various stress-induced kinases.
  • Phosphorylation enhances p53 stability and its ability to transactivate target genes.

Purpose of the Study:

  • To investigate novel kinases that phosphorylate tumor suppressor p53.
  • To identify specific phosphorylation sites on p53 by novel kinases.
  • To explore the role of Cyclin dependent kinase 9 (CDK9) in p53 regulation.

Main Methods:

  • Phosphorylation assays using p53 and CDK9.
  • Site-directed mutagenesis to identify phosphorylation sites.
  • Analysis of p53 phosphorylation at N-terminus (Ser33) and C-terminus (Ser315, Ser392).

Main Results:

  • Cyclin dependent kinase 9 (CDK9) was identified as a novel kinase that phosphorylates p53.
  • Specific phosphorylation sites on p53 by CDK9 were identified: Ser33, Ser315, and Ser392.
  • CDK9's known role as an RNA polymerase II kinase is expanded to include p53 regulation.

Conclusions:

  • CDK9 directly phosphorylates tumor suppressor p53 at novel sites.
  • This phosphorylation event represents a new regulatory mechanism for p53.
  • The biological significance of CDK9-mediated p53 phosphorylation requires further investigation.

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