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A novel function of adenovirus E1A is required to overcome growth arrest by the CDK2 inhibitor p27(Kip1)

K Alevizopoulos1, B Catarin, J Vlach

  • 1Swiss Institute for Experimental Cancer Research (ISREC), CH-1066 Epalinges, Switzerland.

The EMBO Journal
|October 17, 1998
PubMed

Insights

Adenovirus E1A oncoprotein prevents cell growth arrest by p27(Kip1) (p27) and CDK2 inhibitors. E1A acts downstream of p27 and CDK2, interacting with pRb-family proteins to control cell cycle progression.

Area of Science:

  • Molecular Biology
  • Cell Biology
  • Virology

Background:

  • Cell cycle regulation is crucial for preventing uncontrolled cell proliferation.
  • Cyclin-dependent kinases (CDKs) and their inhibitors, like p27(Kip1) and p16(INK4a), are key regulators of cell cycle checkpoints.
  • Adenovirus E1A oncoprotein is known to interfere with host cell cycle control.

Purpose of the Study:

  • To elucidate the mechanism by which adenovirus E1A oncoprotein overcomes cell cycle arrest induced by CDK inhibitors.
  • To determine the specific targets and pathways affected by E1A in relation to p27(Kip1) and CDK2.
  • To investigate the role of pRb-family proteins in E1A-mediated cell cycle bypass.

Main Methods:

  • Fibroblast cell culture and manipulation of oncoprotein expression.
  • Western blotting to assess protein levels and interactions.
  • Inhibition assays using CDK inhibitors (p27, p16, roscovitine) and mutant E1A proteins.
  • Analysis of cell proliferation and gene expression.

Main Results:

  • E1A prevents growth arrest by p27(Kip1) without directly binding p27 or inhibiting CDK2.
  • E1A increases free p27 levels by reducing cyclin D1/D3 expression, yet still promotes proliferation.
  • E1A requires interaction with pRb-family proteins to block p27 and p16(INK4a) induced arrest, but an additional function is needed to bypass CDK2 inhibition.

Conclusions:

  • Adenovirus E1A oncoprotein bypasses cell cycle arrest downstream of p27 and CDK2.
  • E1A utilizes pRb-family proteins and additional effectors to override CDK2-mediated G1-S control.
  • These findings reveal a complex mechanism of viral oncoprotein-induced cell cycle deregulation.

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