Pausing on Polyribosomes: Make Way for Elongation in Translational Control

Among the three phases of mRNA translation—initiation, elongation, and termination—initiation has traditionally been considered to be rate limiting and thus the focus of regulation. Emerging evidence, however, demonstrates that control of ribosome translocation (polypeptide elongation) can also be regulatory and indeed exerts a profound influence on development, neurologic disease, and cell stress. The correspondence of mRNA codon usage and the relative abundance of their cognate tRNAs is equally important for mediating the rate of polypeptide elongation. Here, we discuss recent results showing that ribosome pausing is a widely used mechanism for controlling translation and, as a result, biological transitions in health and disease. Cells regulate protein synthesis through a range of mechanisms, many centered on translation initiation. However, elongation, or ribosome translocation, is emerging as an equally critical stage for translational control.