Translation of messenger RNA into a protein requires recognition of the precise starting point on the mRNA. In eukaryotes that is accomplished by scanning of the small ribosomal subunit along the RNA. A battery of attendant eukaryotic initiation factors is required, two of which (eIF1 and 1A) have been thought to be marginal players in this process. From refined assays of translation initiation, however, it is clear that they are essential.
