Structure/Function of Mammalian Initiation Factors

The initiation phase of protein synthesis in eukaryotic cells is promoted by at least 10 different initiation factor proteins, comprising over 25 distinct polypeptides. The complexity of the process and the finding that these proteins are post-translationally modified by phosphorylation inter al., suggest that rates of translation are controlled by regulating initiation factor activities. In order to better understand the functional roles played by the initiation factors, we and others have purified the proteins from mammalian cells and have begun to elucidate their structures by cloning cDNAs encoding the factors. Possession of cDNA clones provides not only the protein’s sequence, but also tools for cloning the gene and studying its expression, for overexpressing the protein in cells, and for manipulating the protein’s structure. This allows us to study the function of the initiation factors in vivo, thereby providing confirmation of results obtained by in vitro biochemical experiments.