IRF1 and IRF2 are ubiquitously expressed in cells, although they can be upregulated by type I IFNs (36) and, in the case of IRF1, by TLR signaling (48, 49) and HIV-1 infection (45, 50), illustrating how HIV-1 can coopt the antiviral IFN response to augment its own replication. Here, IRF2 is linked to HIV-1 infection.