MULTIPLE GENES ENCODE THE TRANSLATION ELONGATION-FACTOR EF-1-GAMMA INSACCHAROMYCES-CEREVISIAE

A gene encoding a yeast homologue of translation elongation factor 1 g amma (EF-1 gamma), TEF3, was isolated as a gene dosage extragenic supp ressor of the cold-sensitive phenotype of the Saccharomyces cerevisiae drs2 mutant. The drs2 mutant is deficient in the assembly of 40S ribo somal subunits. We have identified a second gene, TEF4, that encodes a protein highly related to both the Tef3p protein (Tef3p), and EF-1 ga mma isolated from other organisms. In contrast to TEF3, the TEF4 gene contains an intron. Gene disruptions showed that neither gene is requi red for mitotic growth. Haploid spores containing disruptions of both genes are viable and have no defects in ribosomal subunit composition or polyribosomes. Unlike TEF3, extra copies of TEF4 do not suppress th e cold-sensitive 40S ribosomal subunit deficiency of a drs2 strain. Lo w-stringency genomic Southern hybridization analysis indicates there m ay be additional yeast genes related to TEF3 and TEF4.