Tales of poly(A): a review.
Until recently, evidence to support a translational role for the 3'-poly(A) tract of eukaryotic mRNAs has been mostly indirect, including: a correlation between the adenylation status of individual mRNAs and their translatability in vivo or in vitro, the demonstration that exogenously added poly(A) is a potent competitive inhibitor of the translation of poly(A)+mRNA, but not poly(A)-mRNAs in vitro, and a correlation between the abundance and stability of poly(A)-binding proteins (PABPs) and the rate of translational initiation in vivo. However, more recent studies demonstrate directly that poly(A)+mRNAs can initiate translation more efficiently than poly(A)-mRNAs, and indicate that this effect is: (i) targeted to the formation of 80S initiation complexes, and (ii) likely to be mediated by the cytoplasmic PABP. We suggest that the 3'-poly(A) tail should be considered a translational enhancer which may stimulate translational initiation in much the same way that transcriptional enhancers are thought to stimulate transcriptional initiation.
Munroe
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Department of Molecular Genetics and Microbiology, University of Massachusetts Medical School, Worcester 01655.
Jacobson
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D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D005786:Gene Expression Regulation; D008957:Models, Genetic; D011061:Poly A / Q000235:genetics* / Q000378:metabolism; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000235:genetics* / Q000378:metabolism
D002352:Carrier Proteins; D012333:RNA, Messenger; D011061:Poly A