19 Identifying Genes Encoding Components of the Protein Synthesis Machinery of the Yeast Saccharomyces cerevisiae

This chapter focuses on identifying genes encoding components of the protein synthesis machinery of the yeast, Saccharomyces cerevisiae. Many of the translation factors identified biochemically in higher eukaryotic cells have now been identified in S. cerevisiae primarily through genetic screens. The chapter summarizes the yeast eIF genes so far identified and their gene products. The unassigned eIF3 subunits have been identified as open reading frames (ORFs), but have not yet been assigned a gene name. The genes encoding the five subunits (eIF2Bα, eIF2Bβ, eIF2Bγ, eIF2Bδ, and eIF2Bɛ) of the eIF2 recycling factor eIF2B have also been identified from the GCN4-based screen. The number of eEF-encoding genes is less than for eIFs, although, in contrast to the eIF-encoding genes, there are generally two copies of each gene. The yeast gene encoding the eEFlB a-subunit remains to be identified. The genes encoding the two essential subunits of the yeast termination release factor (em) have also been identified. The chapter discusses the study of protein synthesis defects in vivo and in vitro and genetic screens used for protein synthesis mutants.