Interrelations between the efficiency of translation start sites and other sequence features of yeast mRNAs.

The translation start site (TSS) plays an important role in the control of the translational efficiency and cytoplasmic stability of eukaryotic mRNAs. The efficiency of TSS recognition is known to be influenced by sequence context, and mRNAs with "weak" TSSs are relatively abundant. We analyzed a sample of 4113 yeast genes in a search for features that might serve to compensate for the inefficient recognition of "weak" TSSs by initiating ribosomes. The first feature found to correlate with variations in TSS strength is differences in the stability of secondary structure upstream and downstream of the start AUG codon. The second feature concerns the characteristics of AUG triplets found at the beginning of the coding sequence, i.e., downstream of the predicted TSS. In particular, the proximal downstream AUG lies in frame with the CDS significantly more often if the TSS itself is located in a "weak" context. The accuracy of TSS annotation, the possibility of polypeptide heterogeneity due to the use of alternative downstream AUGs, and the influence of related features of mRNA sequences are discussed.