Tumor necrosis factor alpha response elements in the HLA-DRA promoter: identification of a tumor necrosis factor alpha-induced DNA-protein complex in astrocytes.
The cytokine tumor necrosis factor alpha (TNF-alpha) alone does not induce class II major histocompatibility complex (MHC) expression in most primary cells but can regulate ongoing class II expression in either a positive or negative fashion. The mechanism(s) by which TNF-alpha enhances interferon gamma (IFN-gamma)-induced class II expression was examined in a primary cell type, the astrocyte, by transient transfection of the HLA-DRA promoter linked to a chloramphenicol acetyltransferase reporter gene (DRA-CAT). We show that TNF-alpha, while having no effect on its own, can synergize with IFN-gamma to increase the level of promoter activity of a DRA-CAT construct. Three known sequences--W, X, and Y--are required for TNF-alpha enhancement of IFN-gamma-induced promoter activity. The corollary effect of TNF-alpha on DNA-binding proteins specific for these elements was examined. A previous report described a DNA-binding protein, IFN-gamma-enhanced factor X (IFNEX), which is upregulated by IFN-gamma in astrocytes and is specific for the X box of the DRA promoter. In this study, we found that TNF-alpha alone did not induce any nuclear proteins; however, combined treatment of astrocytes with both IFN-gamma and TNF-alpha induced a DNA-protein complex of slower electrophoretic mobility than IFNEX. The TNF-alpha-induced complex (TIC-X) has specificity for the X element of the DRA promoter. These results suggest a mechanism by which TNF-alpha enhances IFN-gamma-induced class II MHC expression via the formation of TIC-X.
Panek
R B
RB
Department of Cell Biology, University of Alabama, Birmingham 35294.
Moses
H
H
Ting
J P
JP
Benveniste
E N
EN
D000818:Animals; D001253:Astrocytes / Q000502:physiology* / Q000648:ultrastructure; D001483:Base Sequence; D004252:DNA Mutational Analysis; D004268:DNA-Binding Proteins / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000187:drug effects; D005802:Genes, MHC Class II; D006684:HLA-DR Antigens / Q000235:genetics*; D059805:HLA-DR alpha-Chains; D006801:Humans; D066298:In Vitro Techniques; D007371:Interferon-gamma / Q000494:pharmacology; D007700:Kinetics; D046911:Macromolecular Substances; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009687:Nuclear Proteins / Q000378:metabolism*; D009838:Oligodeoxyribonucleotides / Q000737:chemistry; D011401:Promoter Regions, Genetic; D051381:Rats; D011994:Recombinant Proteins; D017384:Sequence Deletion; D013329:Structure-Activity Relationship; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
D004268:DNA-Binding Proteins; D006684:HLA-DR Antigens; D059805:HLA-DR alpha-Chains; D046911:Macromolecular Substances; D009687:Nuclear Proteins; D009838:Oligodeoxyribonucleotides; D011994:Recombinant Proteins; D014409:Tumor Necrosis Factor-alpha; D007371:Interferon-gamma