22 Translationally Coupled Degradation of mRNA in Eukaryotes

Abstract

The abundance of cytoplasmic messenger RNA in a cell is determined by both the rate of synthesis of the mRNA (i.e., its transcription rate) and the rate at which the mRNA is degraded. Thus, both processes contribute equally to gene expression. If the cell is to change the level of an mRNA rapidly, then it would be advantageous for that mRNA to be short-lived, so that it could respond to rapid changes in transcription. Similarly, a long half-life would be useful if an mRNA was to encode a protein that is needed in great abundance. Therefore, it would seem likely that different mRNAs would have different stabilities, depending on their cellular role.

It is becoming increasingly clear that protein synthesis may have a role in mRNA degradation. There are many examples in which the inhibition of protein synthesis stabilizes mRNA (see below). In principle, this increase in mRNA stability could be a result of the decay of a labile factor, or that the translation machinery itself is involved in the degradation of mRNA. We have limited this discussion to mechanisms of mRNA degradation in eukaryotes; for a recent review of the role of translation in prokaryotic mRNA degradation, see Peterson (1993). In the first part of this chapter, we focus on the degradation of specific mRNAs that carry message instability elements; the second part deals with a global mechanism for degradation of mRNA.

EXAMPLES OF SPECIFIC mRNAS IN WHICH TRANSLATION IS COUPLED TO DEGRADATION
β-Tubulin

One of the best studied...