GATA-6 mediates cell-type specific IFN-γresponse of the HLA-E gene (35.39)

Abstract

Abstract The human MHC Class Ib gene, HLA-E, has been shown to inhibit both Natural Killer cells and a subset of CD8+ cytotoxic T-cells by engaging the CD94/NKG2A inhibitory receptor. IFN-γ induces the expression of HLA-E as well as Class Ia molecules, which are required for killing of target cells. Since HLA-E has negative effects on immune cell killing of target cells, we have sought to identify locus-specific mechanisms of IFN-γ induction in order to identify molecular targets for selective activation of Class Ia genes, but not HLA-E. We have previously identified a unique upstream IFN-γ response region in the HLA-E promoter and showed that GATA-1 is required for its function in the K562 leukemic cell line. We have now examined the effect of GATA family members on IFN-γ induction of HLA-E in other cell types. HLA-E CAT reporter gene assays demonstrated that only epithelial cells which express GATA factors, as determined by western blot and real-time PCR, mediate a 2-to-4 fold enhanced response to IFN-γ stimulation. Functional analysis of HLA-E CAT reporter gene constructs containing mutations of the core nucleotides in the GATA binding site resulted in a four-fold decreased response to IFN-γ. Tetracycline regulated siRNA knockdown of GATA 6 expression in the SKOV3 ovarian carcinoma cell line revealed a two-to-three fold decrease in IFN-γ response of both HLA-E promoter driven constructs and the endogenous HLA-E gene. We conclude that GATA factors play a tissue specific role in regulation of IFN-γ mediated HLA-E expression. This work was supported by National Institutes of Health Grant CA87496 and Immunology Training Grant 5T32AI007407-15.