Tales of poly(A): a review

Area of Science:

• Molecular Biology
• Genetics
• Biochemistry

Background:

• The translational role of the 3'-poly(A) tract in eukaryotic mRNAs was previously supported by indirect evidence.
• Previous studies showed correlations between mRNA adenylation status and translatability, inhibition by exogenous poly(A), and links between poly(A)-binding proteins (PABPs) and translational initiation rates.

Purpose of the Study:

• To provide direct evidence for the translational role of the 3'-poly(A) tail.
• To elucidate the mechanism by which the 3'-poly(A) tail influences mRNA translation.

Main Methods:

• Directly comparing the translation efficiency of poly(A)+mRNAs and poly(A)-mRNAs.
• Investigating the specific stage of translation affected by the poly(A) tail.
• Assessing the involvement of cytoplasmic poly(A)-binding proteins (PABPs).

Main Results:

• Polyadenylated mRNAs (poly(A)+mRNAs) initiate translation more efficiently than non-polyadenylated mRNAs (poly(A)-mRNAs).
• This enhanced translation is specifically targeted to the formation of 80S initiation complexes.
• The effect is likely mediated by cytoplasmic PABPs.

Conclusions:

• The 3'-poly(A) tail functions as a direct translational enhancer for eukaryotic mRNAs.
• This enhancement mechanism involves promoting 80S initiation complex formation, potentially through PABP interaction.
• The poly(A) tail's role in translation initiation is analogous to the function of transcriptional enhancers in gene expression.