Modulation of interferon gene transcription by positive and negative cellular factors

In vivo competition experiments were designed to identify the role of trans-acting cellular factors in the virus-inducible activation of the interferon-beta promoter. Co-transfection of a constant amount of IFN-beta/CAT test gene and increasing amounts of competitive DNA containing different IFN regulatory domains into human epithelioid 293 cells identified a low abundance, positive cellular factor(s) that interacts with the IFN regulatory region. Competition of the factor decreases virus-induced and constitutive level expression of the IFN-beta promoter, and also partially inhibits expression from the SV40 promoter. Negative regulatory effects produced by factors interacting with the IFN upstream region (-135 to -202) and with the SV40 enhancer were also observed.