The involvement of mRNA secondary structure in protein synthesis

Translation initiation in eukaryotes is a complex process involving many factors. A key step in this process is the binding of mRNA to the 43S preinitiation complex. This is generally the rate-limiting step in translation initiation and consequently a major determinant of mRNA translational efficiency. The primary and secondary structure of the mRNA 5' noncoding region have been implicated in modulating translational efficiency. Translational efficiency was shown to be inversely proportional to the degree of secondary structure at the mRNA 5' noncoding region. Furthermore, it was shown that cap-binding proteins that interact with the 5' cap structure (m7GpppN) of eukaryotic mRNAs are involved in the "unwinding" of the mRNA secondary structure, in an ATP hydrolysis mediated event, to facilitate ribosome binding. Thus, cap-binding proteins can potentially regulate mRNA translation. Here, we discuss the available data supporting the notion that eukaryotic 5' mRNA secondary structure plays an important role in translation initiation and the possible regulation of this process.