mRNA Degradation and Decay

International audienceWhy is it important to understand mRNA degradation in a cell? First,RNA degradation has a clearing function and removes RNAs arising from tran-scription, splicing, export, or translation “accidents” to ensure robust geneexpression (see Chap. 8). Second, while regulation of gene expression has a veryimportant transcription component, mRNAs must be turned over rapidly for fastchanges in transcriptome composition. Coordinated destabilization of an entireclass of mRNAs can promote major physiological changes in a cell. Third, specificmechanisms of mRNA decay can serve to regulate gene expression throughfeedback control. Research on these topics has been frequently done first withyeasts and led to a better understanding of gene expression in eukaryotes. We startwith an overview of the methods for measuring mRNA decay on a large scale withan emphasis on how technical issues affect the current picture of global mRNAdecay in yeast. Next, we describe the importance of nuclear degradation in shapingthe stable transcriptome. Once in the cytoplasm, mRNAs are exposed to translationand we provide an overview of the complexes and individual enzymes that ensureprogressive deadenylation, mRNA decapping, and 5 ́ to 3 ́ or 3 ́ to 5 ́ exonucle-olytic RNA degradation. Finally, how organelle transcripts are degraded inmitochondria is briefly exposed