SIGNAL-TRANSDUCTION MECHANISMS IN THE REGULATION OF PROTEIN-SYNTHESIS

Control of polypeptide synthesis plays an important role in cell proli feration and translation rates generally reflect the growth state of t he cultured eukaryotic cell. Physiological regulation of protein synth esis is almost always exerted at the level of polypeptide chain initia tion, with the binding of mRNA to the small ribosomal subunit a rate-l imiting step in many cell systems. Studies have indicated key roles in the regulation of protein synthesis for the structural features of mR NA molecules and phosphorylation of initiation factors which catalyse this process. This review focusses on translational regulation at the level of mRNA binding to the ribosome and the role of phosphorylation of initiation factors in mediating both quantitative and qualitative c ontrol. The identity of putative kinases which may mediate these proce sses is addressed and a possible model for the role of a transient act ivation of initiation factors in cell growth or differentiation is pre sented.