6 Control of Messenger RNA Stability during Development

This chapter focuses on the regulation of mRNA stability in embryonic development and cell differentiation. It is indicated that the mechanism of action varies for different mRNAs and in different organisms. Cis-acting elements that mediate mRNA degradation are frequently located in the 3' untranslated regions (UTRs) of mRNAs. In some cases, these regulatory elements appear to activate RNA degradation through deadenylation, as for the Drosophila bicoid and hunchback mRNAs, the C. elegans fern-3 mRNA, the Xenopus for Eg2 mRNA, and the plant transmitting-tissue specific (TTS) mRNAs. For many mRNAs, the translational status seems to be critical for the control of mRNA decay as evidenced by the stabilization of some mRNAs by a premature stop codon. In other cases, inhibitors of protein synthesis block mRNA decay and this may mean either that ribosome transit on the specific mRNA is necessary or that degradation depends on the continuous synthesis of an essential transfactor. Some progress has recently been made in the identification of trans-acting factors that recognize regulatory sequences in the target RNA. Drosophila and C. elegans genetics have been instrumental in the identification of such factors, and some interesting insights regarding the similarities and differences between these organisms have emerged.