Nucleotides upstream of the Kozak sequence strongly influence gene expression in the yeast S. cerevisiae

Background In the yeast Saccharomyces cerevisiae, as in every eukaryotic organism, the mRNA 5′-untranslated region (UTR) is important for translation initiation. However, the patterns and mechanisms that determine the efficiency with which ribozomes bind mRNA, the elongation of ribosomes through the 5′-UTR, and the formation of a stable translation initiation complex are not clear. Genes that are highly expressed in S. cerevisiae seem to prefer a 5′-UTR rich in adenine and poor in guanine, particularly in the Kozak sequence, which occupies roughly the first six nucleotides upstream of the START codon.