Mechanisms and control of mRNA turnover in Saccharomyces cerevisiae

mRNA turnover makes significant contributions to the control of gene expression. Recent studies of mRNA turnover in the simple eukaryote Saccharomyces cerevisiae have led to a better understanding of this process. These studies suggest that half-lives of individual transcripts are determined in large part by the interplay between specific sequences within mRNAs and less defined features of an mRNA, such as translation rate. These studies also indicate that yeast mRNAs are degraded through a diverse set of decay pathways. The most common of these pathways is deadenylation-dependent decapping, in which transcripts are deadenylated, thereby promoting decapping and exposing the transcript to 5'-to-3' exonucleolytic digestion. Additional pathways of mRNA decay include deadenylation-independent decapping 3'-to-5' degradation and possibly endonucleolytic cleavage. Recent experiments have also begun to identify some of the trans-acting factors responsible for both performing and regulating the nucleolytic events in these various pathways. Further identification of additional trans-acting factors that function in mRNA decay and the development of yeast cell-free systems capable of reproducing in vivo mRNA turnover are major challenges to be addressed.