Locus-specific constitutive and cytokine-induced HLA class I gene expression.
Cytokine induction of the MHC class I genes increases the nascent molecules available for binding potentially antigenic peptides. The human H chain loci, HLA-A, -B, and -C, encode highly homologous and polymorphic mRNAs. Here, these transcripts were resolved and measured by competitive PCR of cDNA using locus-specific primers. Endothelial cells expressed many HLA-A and -B, but fewer HLA-C, transcripts. In contrast, HeLa cells expressed many HLA-A and -C, but fewer HLA-B, transcripts. The inflammatory cytokines TNF-alpha, IFN-beta, and IFN-gamma induced HLA-B strongly, but HLA-A and -C weakly in both cell types. Combined treatment with IFNs and TNF further increased HLA-A and -B, but not HLA-C transcripts. The constitutive and inducible activities of transfected promoters correlated well with mRNA levels. The weak IFN response of the HLA-A2 promoter was not due to variations in the IFN consensus sequence, the site alpha, or a 3-bp insertion between them. The HLA-Cw6 promoter was less TNF responsive due to a variant kappaB enhancer, which also reduced the IFN responses. The NF-kappaB subunit RelA strongly activated the HLA-A2 and -B7 promoters but only weakly activated the HLA-Cw6 promoter due to the variant kappaB. Cotransfecting NF-kappaB1 with RelA further increased activity of the HLA-A2 and -B7, but not HLA-Cw6, promoters. All three promoters were activated by MHC class II trans-activator, but not CREB-binding protein, whereas IFN regulatory factor-1 and -2 weakly activated the HLA-B7 and -Cw6, but not HLA-A2, promoters. These studies illustrate common and locus-specific mechanisms that may be targeted to modulate immune reactions.
Johnson
David R
DR
Department of Pathology, Yale University School of Medicine, New Haven, CT 06510, USA. drjohnson@niaid.nih.gov
D001483:Base Sequence; D002460:Cell Line; D002461:Cell Line, Transformed; D002462:Cell Membrane / Q000276:immunology / Q000378:metabolism; D002478:Cells, Cultured; D003001:Cloning, Molecular; D016207:Cytokines / Q000502:physiology*; D004730:Endothelium, Vascular / Q000166:cytology / Q000276:immunology / Q000378:metabolism; D005786:Gene Expression Regulation / Q000276:immunology*; D005819:Genetic Markers / Q000276:immunology; D006680:HLA Antigens / Q000096:biosynthesis* / Q000235:genetics*; D006367:HeLa Cells; D015395:Histocompatibility Antigens Class I / Q000096:biosynthesis* / Q000235:genetics*; D006801:Humans; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic / Q000276:immunology; D012333:RNA, Messenger / Q000096:biosynthesis; D014157:Transcription Factors / Q000096:biosynthesis / Q000502:physiology; D014162:Transfection
D016207:Cytokines; D005819:Genetic Markers; D006680:HLA Antigens; D015395:Histocompatibility Antigens Class I; D012333:RNA, Messenger; D014157:Transcription Factors