Diverse roles for ISGs in the IFN antiviral pathway
Incoming viruses are sensed by pattern recognition receptors (PRR), leading to activation of interferon regulatory factors (IRFs) and transcriptional induction of IFNs. Antiviral IFNs signal through the JAK/STAT pathway to induce ISG production. ISGs can also be directly induced by some IRFs in an IFN-independent pathway (thin blue arrow). Some ISGs function to block virus replication (thick red bars), while others have the ability to promote or enhance replication of certain viruses (green arrow). A subset of ISGs are themselves components of the IFN pathway or promote its signaling (red dotted arrows). IFN also induces several negative regulators that can target PRR, IRFs, or JAK/STAT to dampen the response (thin red bars).