Kinetically coordinated induction of TAP1 and HLA class I by IFN-γ: the rapid induction of TAP1 by IFN-γ is mediated by Stat1 α

Transporter associated with Ag processing-1 (TAP1) is induced by IFN-gamma more rapidly than is HLA class I. Kinetic analysis of transfectants reveals that IFN-gamma activates the TAP1 promoter more rapidly than the HLA-B7 class I promoter. A gamma-activating sequence (GAS) in the TAP1 promoter is necessary for the rapid induction by IFN-gamma. Two overlapping IFN consensus sequences contribute to the constitutive and TNF-induced expression of TAP1 but are not necessary for the IFN-gamma response. Moreover, IFN-gamma activates the GAS-binding protein Stat1 alpha much more rapidly than it induces the IFN consensus sequence-binding protein IRF-1, which mediates the response of the HLA-B7 class I promoter. We conclude that IFN-gamma uses different transcription factors to regulate the sequence of appearance of these interacting gene products.