Messenger RNA degradation in Saccharomyces cerevisiae

The analysis of 17 functional mRNAs and two recombinant mRNAs in the yeast Saccharomyces cerevisiae suggests that the length of an mRNA influences its half-life in this organism. The mRNAs are clearly divisible into two populations when their lengths and half-lives are compared. Differences in ribosome loading amongst the mRNAs cannot account for this division into relatively stable and unstable populations. Also, specific mRNAs seem to be destabilized to differing extents when their translation is disrupted by N-terminus-proximal stop codons. The analysis of a mutant mRNA, generated by the fusion of the yeast PYK1 and URA3 genes, suggests that a destabilizing element exists within the URA3 sequence. The presence of such elements within relatively unstable mRNAs might account for the division between the yeast mRNA populations. On the basis of these, and other previously published observations, a model is proposed for a general pathway of mRNA degradation in yeast. This model may be relevant to other eukaryotic systems. Also, only a minor extension to the model is required to explain how the stability of some eukaryotic mRNAs might be regulated.