PARTICIPATION OF INITIATION-FACTORS IN THE RECRUITMENT OF MESSENGER-RNA TO RIBOSOMES

The step of protein synthesis which is normally rate limiting, formati on of the 48S initiation complex, is catalyzed by the group 4 initiati on factors. Collectively they recognize the 7-methylguanosine-containi ng cap of mRNA, unwind mRNA secondary structure, and allow scanning fo r the initiation codon by the small ribosomal subunit. The activities of the eIF-4 polypeptides are modulated by phosphorylation. Recent stu dies shed new light on the mechanism of assembly of the 48S initiation complex and the effect of phosphorylation of one of the eIF-4 polypep tides, the cap-binding protein eIF-4E.