Sequence and structural features associated with translational initiator regions in yeast--a review

We have compared the translational initiator regions of 131 yeast genes. 95% utilize the first AUG from the 5' end of the message as the start codon for translation. Yeast leader regions in general are rich in adenine nucleotides (nt), have an average length of 52 nt, and are void of significant secondary structure. Sequences immediately adjacent to AUG start codons are preferred, however, the bias in nucleotide distribution (5'-A-YAA-UAAUGUCU-3') does not reflect a higher eukaryotic consensus (5'-CACCAUGG-3') with the exception of an adenine nucleotide preference at the -3 position. A minority of yeast mRNAs that contain AUG codons in the leader region that do not serve as the start codon for the primary gene product differ from the majority of mRNAs by one or more of these general properties. This analysis appears to indicate that basic features associated with yeast leader regions are consistent with a general mechanism of initiation of protein synthesis in eukaryotes, as proposed by the ribosomal 'scanning' model, but perhaps only basic features associated with ribosomal recognition of an AUG start codon are intact.