A candidate interferon-gamma activated site (GAS element) in the HLA-G promoter does not bind nuclear proteins.
The HLA-G gene is highly expressed at the maternal-fetal interface, where it is believed to participate in the generation and maintenance of maternal tolerance to the fetal semiallograft. This gene has two elements through which interferon-gamma (IFN-gamma) could act to enhance its rate of transcription, an Enhancer A/ICS region and a candidate IFN-gamma activated site (GAS). In this study we investigated functionality of this candidate HLA-G GAS. Two HLA-G-expressing cell lines were tested, the human myelomonocytic cell line, U937, and a mouse fibroblast cell line, S14/8, which is stably transfected with the full length HLA-G gene. Nuclear proteins from IFN-gamma-treated U937 and S14/8 cells bound the interferon regulatory factor-1 (IRF-1) gene GAS sequence (TTC CCCGAA) but not the HLA-G gene's candidate GAS sequence (TTTCGAGAA). Excess unlabeled HLA-G-GAS oligonucleotide failed to inhibit binding of the IRF-1-GAS using the same nuclear extracts. These data indicate that a sequence in the HLA-G gene which would normally permit cytokine enhancement of gene expression, the GAS element, is nonfunctional. This is also true of another regulatory sequence, the Enhancer A/ICS element, suggesting that defects in IFN-gamma response elements prevent inappropriate up-regulation of HLA-G gene expression at the maternal-fetal interface.
Chu
W
W
Department of Anatomy and Cell Biology, University of Kansas Medical Center, Kansas City 66160, USA.
Gao
J
J
Murphy
W J
WJ
Hunt
J S
JS
D000818:Animals; D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics; D002460:Cell Line; D004247:DNA / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics; D005260:Female; D005809:Genes, Regulator; D006680:HLA Antigens / Q000235:genetics*; D059951:HLA-G Antigens; D015395:Histocompatibility Antigens Class I / Q000235:genetics*; D006801:Humans; D050856:Interferon Regulatory Factor-1; D007371:Interferon-gamma / Q000494:pharmacology*; D008431:Maternal-Fetal Exchange / Q000235:genetics / Q000276:immunology; D051379:Mice; D009687:Nuclear Proteins / Q000378:metabolism; D010750:Phosphoproteins / Q000235:genetics; D011247:Pregnancy; D011401:Promoter Regions, Genetic; D011994:Recombinant Proteins; D014162:Transfection; D020298:U937 Cells
D004268:DNA-Binding Proteins; D006680:HLA Antigens; D059951:HLA-G Antigens; D015395:Histocompatibility Antigens Class I; C494257:IRF1 protein, human; D050856:Interferon Regulatory Factor-1; C494258:Irf1 protein, mouse; D009687:Nuclear Proteins; D010750:Phosphoproteins; D011994:Recombinant Proteins; D007371:Interferon-gamma; D004247:DNA