Fig 7.

Inhibition of IFN induction by paramyxovirus V proteins. Paramyxovirus V proteins block both mda-5-dependent and RIG-I-dependent IFN induction. Replication potentially generates ligands for both mda-5 and RIG-I, and transcription of the PIV5 L gene has been shown to generate a ligand for mda-5 (26). Inhibition of mda-5 occurs through a direct interaction between V and mda-5 which prevents ligand binding and consequent activation of the signaling pathway leading to IRF-3 and NF-κB activation. V proteins inhibit RIG-I signaling by interacting with LGP2 and promoting the formation of an inhibitory complex between RIG-I and LGP2 which is refractory to activation by viral RNA.