Comparison of the capacity of different viral internal ribosome entry segments to direct translation initiation in poly(A)-dependent reticulocyte lysates.

Polyadenylation stimulates translation of capped eukaryotic mRNAs and those carrying picornaviral internal ribosome entry segments (IRESes) in vivo. Rabbit reticulocyte lysates (RRL) reproduce poly(A)-mediated translation stimulation in vitro after partial depletion of ribosomes and ribosome-associated factors. Here, we have evaluated the effects of varying different parameters (extent of extract depletion, cleavage of eIF4G, concentrations of KCl, MgCl(2) and programming mRNA) on IRES-driven translation efficiency and poly(A)-dependency in ribosome-depleted RRL.

Free poly(A) stimulates capped mRNA translation in vitro through the eIF4G-poly(A)-binding protein interaction.

The 5' cap and 3' poly(A) tail of classical eukaryotic mRNAs functionally communicate to synergistically enhance translation initiation. Synergy has been proposed to result in part from facilitated ribosome recapture on circularized mRNAs. Here, we demonstrate that this is not the case.