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

New synthetic eukaryotic promoters, which differ for their translation initiation rate, can be built by acting on the nucleotides upstream of the Kozak sequence. Translation efficiency could, potentially, be influenced by another portion of the 5'-UTR further upstream of the START codon. A deeper understanding of the role of the 5'-UTR in gene expression would improve criteria for choosing and using promoters inside yeast synthetic gene circuits.