The Translation Efficiency of Ovalbumin mRNA Is Determined in Part by a 5′-End Hairpin Structure

We have investigated the role in translation of the secondary structure in the noncoding leader (NCL) sequence of ovalbumin mRNA. Deletion of a stem-loop structure from the mRNA 5′-end (hairpin-1) produced a 2.5-fold decrease in mRNA translation rate in both rabbit reticulocyte and wheat germ cell-free systems. A corresponding 2-fold reduction in mRNA binding affinity for reticulocyte eucaryotic initiation factor 2 (eIF-2) was also observed. These effects were independent of mRNA capping. Both translation rate and eIF-2 binding affinity were restored by addition to the mRNA of a sequence containing a hairpin-1-like structure. The positive correlation between cell free translation rate and mRNA binding to eIF-2 suggests that hairpin-1 is both an initiation signal and part of a specific eIF-2 recognition site. Methylation interference indicated a direct interaction between eIF-2 and hairpin-1 of ovalbumin mRNA.