ABSTRACT
Eukaryotic gene expression involves a number of interlinked post-transcriptional steps that are subject to surveillance or quality control mechanisms to ensure that only fully processed and error-free mRNAs are translated. Among these, the nonsense-mediated mRNA decay (NMD) pathway recognizes and targets for degradation mRNAs containing premature translation termination codons (PTCs), which could give rise to truncated and potentially harmful proteins. The NM D pathway not only prevents the accumulation of malfunctioning proteins but also modulates the clinical manifestations of many human ge netic disorders (see chapters by Holbrook et al and Keeling et al). A cross-species analysis of this pathway has revealed important conserved key components, and has provided the basis for elucidating the N M D network in humans. This chapter focuses on the NM D pathway in the fruitfly Drosophila melanogaster, emphasizing how studies in this model organism have provided new insights into the mechanisms underlying NM D and its evolution.
