Poly(A)-Binding Protein Regulates the Efficiency of Translation Termination

Area of Science:

• Molecular Biology
• Genetics
• Yeast Biology

Background:

• Translation termination efficiency is influenced by various factors, including codon identity and sequence context.
• The precise role of nonsense codon location within an open reading frame (ORF) on termination efficiency remains to be fully elucidated.

Purpose of the Study:

• To investigate whether the relative position of a premature termination codon (PTC) within an ORF affects translation termination efficiency.
• To explore the involvement of poly(A)-binding protein (PABP) in regulating translation termination.

Main Methods:

• Quantification of prematurely terminated and readthrough polypeptides from 26 nonsense alleles across 3 yeast genes.
• Analysis of termination efficiency in relation to PTC proximity to the mRNA 3' end.
• Assessment of termination efficiency in yeast cells with mutations in poly(A)-binding protein (pab1).

Main Results:

• Premature termination product accumulation and readthrough extent showed a strong dependence on PTC proximity to the mRNA 3' end.
• Premature termination products increased, while readthrough efficiencies decreased as PTCs moved further from the 3' end.
• Readthrough efficiencies increased with 3' untranslated region (UTR) lengthening, and these effects were abolished in pab1 mutant cells.

Conclusions:

• Poly(A)-binding protein plays a critical role in regulating translation termination efficiency.
• Inefficient translation termination may act as a trigger for nonsense-mediated mRNA decay (NMD).