The Saccharomyces cerevisiae HCR1 gene encoding a homologue of the p35 subunit of human translation initiation factor 3 (eIF3) is a high copy suppressor of a temperature-sensitive mutation in the Rpg1p subunit of yeast eIF3

The complex eukaryotic initiation factor 3 (eIF3) was shown to promote the formation of the 43 S preinitiation complex by dissociating 40 S and 60 S r ibosomal subunits, stabilizing the ternary complex, and aiding mRNA binding to 40 S ribosomal subunits. Recently, we described the identification of R PG1 (TIF32), the p110 subunit of the eIF3 core complex in yeast. In a scree n for Saccharomyces cerevisiae multicopy suppressors of the rpg1-1 temperat ure-sensitive mutant, an unknown gene corresponding to the open reading fra me YLR192C was identified. When overexpressed, the 30-kDa gene product, nam ed Hcr1p, was able to support, under restrictive conditions, growth of the rpg1-1 temperature-sensitive mutant, but not of a Rpg1p-depleted mutant. An hcr1 null mutant was viable, but showed slight reduction of growth when co mpared with the wild-type strain. Physical interaction between the Hcr1 and Rpg1 proteins was shown by co-immunoprecipitation analysis. The combinatio n of Delta hcr1 and rpg1-1 mutations resulted in a synthetic enhancement of the slow growth phenotype at a semipermissive temperature. In a computer s earch, a significant homology to the human p35 subunit of the eIF3 complex was found. We assume that the yeast Hcr1 protein participates in translatio n initiation likely as a protein associated with the eIF3 complex.