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Human carbon catabolite repressor protein (CCR4)-associative factor 1: cloning, expression and characterization of

J A Bogdan1, C Adams-Burton, D L Pedicord

  • 1DuPont Pharmaceuticals Company, Experimental Station E400-3231, Wilmington, DE 19880-0400, USA.

The Biochemical Journal
|November 20, 1998
PubMed

Insights

The BTG1 tumor suppressor protein interacts with human CAF-1 (hCAF-1) after BTG1 phosphorylation at Ser-159. This complex formation is crucial for regulating cell proliferation during cell-cell contact.

Area of Science:

  • Molecular Biology
  • Cell Biology
  • Biochemistry

Background:

  • The tumor suppressor protein BTG1 inhibits cell proliferation, but its mechanism of action is unclear.
  • Understanding BTG1's interactions is key to elucidating its anti-proliferative role.

Purpose of the Study:

  • To identify proteins that interact with human BTG1 (hBTG1).
  • To investigate the role of the BTG1-interacting protein complex in cell proliferation control.

Main Methods:

  • Yeast two-hybrid screening to identify hBTG1 interacting partners.
  • In vitro kinase assays to determine phosphorylation requirements for complex formation.
  • Cell synchrony, Western blot, and co-immunoprecipitation in rat aortic smooth-muscle cells (RSMCs).
  • Overexpression studies in NIH 3T3 and U-2-OS cells.

Main Results:

  • Human carbon catabolite repressor protein 4-associative factor 1 (hCAF-1) was identified as an hBTG1 interacting partner.
  • hCAF-1/BTG1 complex formation is dependent on BTG1 phosphorylation at Ser-159 by specific cell cycle kinases (CDK2/cyclin E and CDK2/cyclin A).
  • Rat CAF-1 (rCAF-1) and BTG1 are upregulated and physically associate in the nucleus of contact-inhibited RSMCs.
  • Overexpression of hCAF-1 exhibits anti-proliferative effects in NIH 3T3 and U-2-OS cells.

Conclusions:

  • Phosphorylation of BTG1 at Ser-159 is essential for its interaction with hCAF-1.
  • The hCAF-1/BTG1 complex plays a significant role in the signaling pathways that regulate cell proliferation in response to cell-cell contact.

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