Turnover of mRNA in prokaryotes and lower eukaryotes.

The turnover of mRNA plays an important role in the regulation of gene expression. The two best understood model systems are those of the prokaryote Escherichia coli and the lower eukaryote Saccharomyces cerevisiae. Considerable progress in recent years has helped define the general pathways by which mRNA is degraded in E coli. Much less is known about the pathways of decay, or the enzymes involved, in eukaryotic cells. However, both cis-acting sequences and trans-acting factors have recently been characterized in S. cerevisiae and an indispensable role for translation has been identified. A comparison of these model species highlights both similarities and differences in mRNA turnover between prokaryotic and eukaryotic systems.