Protein binding in an mRNA 5'-UTR sterically hinders translation.

Structures in the 5' untranslated regions (UTRs) of mRNAs can physically modulate translation efficiency by impeding the scanning ribosome or by sequestering the translational start site. We assessed the impact of stable protein binding in 5'- and 3'-UTRs on translation efficiency by targeting the MS2 coat protein to a reporter RNA via its hairpin recognition site. Translation was assessed from the reporter RNA when co-expressed with MS2 coat proteins of varying affinities for the RNA, and at different expression levels.