Figure 8. Model for early and late UPF3B function in translation termination.

During termination at a PTC ribosome‐bound UPF3B interacts with the eRF1/eRF3a‐GTP complex impeding efficient stop codon recognition. UPF1 bound to the 3′UTR can contact the termination complex, but does not interfere with termination. After GTP hydrolysis and peptide release UPF3B destabilizes the post‐termination ribosomal complex leading to its dissociation. Subsequently, UPF3B, UPF1, UPF2 and other factors activate UPF1's ATPase and helicase functions to remodel the 3′UTR mRNP and attract decay enzymes.