Two internal ribosome entry sites mediate the translation of p53 isoforms

Area of Science:

• Molecular Biology
• Cell Biology
• Cancer Research

Background:

• The p53 protein is a critical tumor suppressor involved in cell cycle arrest and apoptosis.
• A previously identified p53 isoform, DeltaN-p53, is produced via internal translation initiation and inhibits full-length p53 activity.

Purpose of the Study:

• To investigate the mechanisms of translational control for both full-length and DeltaN-p53 isoforms.
• To identify the regulatory elements responsible for differential isoform production.

Main Methods:

• Analysis of internal ribosome entry sites (IRESs) in p53 mRNA.
• Characterization of IRES activity across different cell cycle phases.

Main Results:

• Two distinct IRES elements were identified that mediate translation of p53 isoforms.
• The IRES for full-length p53 is located in the 5'-untranslated region.
• The IRES for DeltaN-p53 spans into the protein-coding region.
• Differential cell-cycle-dependent activity was observed: full-length p53 IRES active at G2-M, DeltaN-p53 IRES active at G1-S.

Conclusions:

• Novel translational control mechanisms regulate p53 gene expression.
• Distinct IRES activities contribute to the cell-cycle-dependent balance of p53 isoforms.
• This provides new insights into the regulation of p53 function in cellular processes.