PABP and the poly(A) tail augment microRNA repression by facilitated miRISC binding

Area of Science:

• Molecular Biology
• Gene Regulation
• RNA Biology

Background:

• Polyadenylated mRNAs are generally repressed more effectively by microRNAs (miRNAs) than nonadenylated mRNAs.
• The poly(A) tail and associated proteins play a role in mRNA regulation and stability.

Purpose of the Study:

• To investigate the mechanism by which polyadenylation enhances miRNA-mediated translational repression.
• To elucidate the role of the poly(A)-binding protein (PABP) in this process.

Main Methods:

• Utilized a cell-free translation system from Drosophila melanogaster.
• Investigated the correlation between poly(A) tail length and miRNA repression efficiency.
• Examined the effect of the GW182 silencing domain versus the miRNA-induced silencing complex (miRISC) on repression.
• Monitored PABP and miRISC association with mRNA.

Main Results:

• miRNA repression strength positively correlated with poly(A) tail length.
• The stimulatory effect of the poly(A) tail on repression was dependent on the miRNA-induced silencing complex (miRISC) and not solely on the GW182 silencing domain.
• Poly(A)-binding protein (PABP) was found to promote the association of miRISC with miRNA-regulated mRNAs.
• PABP dissociation from mRNA occurred rapidly upon miRISC recruitment and preceding detectable deadenylation.

Conclusions:

• Poly(A)-binding protein (PABP) is a key mediator of enhanced miRNA repression for polyadenylated mRNAs.
• PABP facilitates miRISC recruitment to target mRNAs, thereby increasing translational repression efficiency.
• A revised model for PABP and poly(A) tail function in miRNA-mediated translational repression is proposed.