Figure 3.

Interactions between UPF proteins and termination machinery.Left, a terminating ribosome. Right, a recycling ribosome. The UPF proteins interact with the ribosome and termination factors in both a direct (black lines) and indirect (purple lines) fashion. All three UPF proteins can interact with the 80S ribosome and the 40S subunit although the specific contacts within these assemblies are known only for UPF1. All three UPF proteins are also reported to interact with termination factors. The numbers on each arrow represent possible functions of each interaction listed in the legend below. References that provide evidence for the interactions between UPF proteins and termination machinery are included in parentheticals.