Theinterferon-bpromoter has been studied extensively as a model system for combinatorial transcriptional regulation. Invirus-infectedcells the transcription factorsATF-2, c-Jun, interferon regulatory factor (IRF)-3, IRF-7andNF-jB, and the coactivators p300/CBP play critical roles in the activa-tion of this and other promoters. It remains unclear, how-ever, why most other combinations of AP-1, IRF and Rel proteins fail to activate theinterferon-bgene. Here we have explored how different IRFs may cooperate with other fac-tors to activate transcription
