Background
In humans, NMD depends on RNA-dependent ATPase and 5' to 3' helicase UPF1, plus six other proteins designated SMG1, SMG5, SMG6, SMG7, UPF2 and UPF3. SMG5, SMG7 and UPF1 localize to cytoplasmic foci called P-bodies, while SMG5, SMG6 and SMG7 target UPF1 for dephosphorylation. SMG7 may also act as an adaptor in targeting mRNAs associated with phosphorylated UPF1 for degradation. SMG7 provides a link between the NMD pathway and mRNA degradation machinery by forming a complex with the proteins SMG5 and UPF1, interacting with them via its N-terminal domain, and targeting bound reporter transcripts for decay via its C-terminal domain. SMG7 contains a 14-3-3-like domain, and residues that bind phosphoserine-containing peptides in 14-3-3 proteins are conserved at the equivalent positions in SMG7.