Table 4 Brief summary of factors known to act in C. elegans translational surveillance
C. elegansHuman OrthologDomainsDescription
Nonsense-mediated decay
smg-1SMG1PI3KinaseSMG-1 encodes a huge protein with a PI3K domain required for NMD, presumably via phosphorylation of SMG-2
smg-2UPF1RNA helicase, AAABinds mRNAs and is dynamically phosphory-lated/dephosphorylated, with the phosphorylated form exhibiting a preference for NMD targets. Binding observed throughout 3′UTRs.
smg-3UPF2MIF4G, Upf2SMG-2/3/4 interact and are thought to constitute a “core” NMD complex conserved in most eukaryotes.
smg-4UPF3A and UPF3BUpf3SMG-2/3/4 interact and are thought to constitute a “core” NMD complex conserved in most eukaryotes.
smg-5SMG5PIN (catalytically inactive)With SMG-7, required for efficient dephosphorylation of SMG-2
smg-6SMG6EST1, PINSMG-6 contains a PIN endoribonuclease domain required for NMD
smg-7SMG7EST1With SMG-5, required for efficient dephosphorylation of SMG-2
smgl-1NBASWD40Identified alongside smgl-2; loss-of-function via RNAi stabilizes some NMD targets. Complete loss-of-function thought to be lethal.
smgl-2DHX34DExH-box helicaseIdentified alongside smgl-1; loss-of-function via RNAi stabilizes some NMD targets. Complete loss-of-function thought to be lethal.
Nonstop/no-go decay
skih-2SKIV2LDEAD-box helicase, rRNA processing ArchCatalytic subunit of the SKI RNA helicase and is required for 3′>5′ decay of Nonstop mRNAs
ttc-37TTC37Tetratricopeptide repeatScaffolding subunit of the SKI RNA helicase and is required for 3′>5′ decay of Nonstop mRNAs
pelo-1PELOeRF1 domains 1, 2, and 3Ribosome rescue factor required for release of ribosomes from Nonstop mRNAs; homologous to eRF1
nonu-1N4BP2P-loop Kinase, Cue, SmrPutative endoribonuclease required for repression of Nonstop and No-Go mRNAs
  • This table describes factors currently known to act in translational surveillance in C. elegans. This list is not exhaustive, esp. for Nonstop/No-Go Decay where genetic screens for factors are far from saturated and several more factors are known in systems other than C. elegans. There is an extensive literature for many of these individual factors, and readers are referred to references and reviews for further reading (see main text).