Figure 1.

Triggering and Regulating NMD. RNA degradation elicited by the NMD pathway depends on UPF proteins and is enhanced by the exon junction complex (EJC), whose core components are outlined in gray. UPF3B is thought to be critical for NMD because it drives the interaction of the EJC with the NMD adaptor protein, UPF2, and the RNA helicase UPF1. UPF3A has the opposite function – it represses NMD.⁴⁵