Fig. 2.

Endogenous IRF7 is a short-lived protein relative to long-lived IRF3. (A) MEFs were left untreated (No IFN) or were treated overnight with IFNα/β prior to incubation with CHX for the indicated times (h). Protein extracts were assayed for IRF7 (left panel) or IRF3 (right panel) by western blotting and densitometric quantitation (graphs) for calculation of half-lives. Note that no IRF7 was detectable in cells without IFN treatment. IRF7 and IRF3 half-lives were calculated for mouse thymocytes (B) and splenocytes (C) as described in (A), except that it was not necessary to pretreat cells with IFN.