UPF1 P-body localization.

NMD (nonsense-mediated mRNA decay) is a mechanism that degrades transcripts containing PTCs (premature translation termination codons). NMD is a translation-associated process that is expected to take place throughout the cytoplasm. However, recent studies have indicated that the core NMD factors UPF1 (up-frameshift-1), UPF2 and UPF3 can associate with P-bodies (processing bodies), which are large cytoplasmic granules replete with proteins involved in general mRNA decay and related processes. It has been proposed that UPF1 directs PTC-containing mRNAs to P-bodies and triggers decay. Here, we discuss the link between P-bodies and NMD in view of recent studies that suggest that P-bodies are not required for NMD in Drosophila.