Differential regulation of HLA class I genes by interferon

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Abstract
Allele-specific differences in the regulation of HLA class I genes by type I interferon (IFN) were observed after transfection of eight HLA-B,-A, or-C genes into mouse L cells. HLA-B7 and -Bw64 gene expression was significantly more inductible by type I IFN than the genes coding for HLA-B27, HLA-B51, HLA-B38, HLA-B39, HLA-Cw3, and HLA-A2 antigens. Modification of the 5′ end of HLA-B7 and HLA-B27 genes revealed the presence of enhancer sequences responding to IFN treatment in the 5′ untranslated region of HLA-B7, but not of HLA-B27 and suggested further, independently acting enhancer elements downstream of the transciption initiation site. Comparison of 5′ enhancer region sequences in correlation with type I IFN inducibility of the different HLA class I alleles indicated that the exchange of only two nucleotides in the interferon response sequence (IRS) or enhancer A region of HLA-B7 or -Bw64 could account for nonregulated promoters in all other HLA-A,-B or -C alleles analyzed. Thus, type I IFN stimulation of HLA class I genes in mouse L cells appears to predominantly operate in most alleles by a mechanism targeted to enhancer sequences downstream of the gene's transcription initiation site.