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p16(INK4A) positively regulates p21(WAF1) expression by suppressing AUF1-dependent mRNA decay

Huda H Al-Khalaf1, Abdelilah Aboussekhra

  • 1Department of Molecular Oncology, King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia.

Plos One
|July 30, 2013
PubMed
Abstract

Insights

The tumor suppressor p16(INK4a) stabilizes the CDKN1A mRNA by inhibiting the AUF1 protein, thereby increasing p21(WAF1) expression. This reveals a direct link between the pRB/p16(INK4a) and p53/p21(WAF1) cancer pathways.

Area of Science:

  • Molecular Biology
  • Cancer Biology
  • Cell Cycle Regulation

Background:

  • p16(INK4a) and p21(WAF1) are key tumor suppressors regulating cell cycle, senescence, and apoptosis.
  • Both proteins are crucial in anti-cancer processes and are encoded by CDKN2A and CDKN1A genes, respectively.

Purpose of the Study:

  • To elucidate the molecular mechanisms connecting p16(INK4a) and p21(WAF1).
  • To investigate how p16(INK4a) influences p21(WAF1) expression and its role in cancer pathways.

Main Methods:

  • Utilized immunoprecipitation and quantitative RT-PCR to analyze AUF1-CDKN1A mRNA interactions.
  • Employed silencing RNAs (siRNAs) for gene knockdown experiments.
  • Used EGFP reporter assays to study AU-rich element (ARE) dependent regulation.
  • Conducted ectopic expression studies in p16(INK4a)-deficient cells.

Main Results:

  • p16(INK4a) positively controls p21(WAF1) expression in human and mouse cells.
  • p16(INK4a) stabilizes CDKN1A mRNA by negatively regulating the decay-promoting protein AUF1.
  • AUF1 directly binds to CDKN1A mRNA in a p16(INK4A)-dependent manner.
  • Knockdown of AUF1 increased CDKN1A mRNA levels, while concurrent knockdown of AUF1 and CDKN2A restored normal gene expression.

Conclusions:

  • p16(INK4a) stabilizes CDKN1A mRNA via AUF1 inhibition, confirming a direct link between pRB/p16(INK4A) and p53/p21(WAF1) cancer pathways.
  • Findings highlight a novel regulatory mechanism involving p16(INK4a), AUF1, and p21(WAF1) in tumor suppression.

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