Alternative splicing of HLA class I transcripts induced by IFN-gamma and TNF in fibroblasts: release of soluble HLA class I heavy chain and an associate protein.
FS-4 fibroblasts were found to produce 37-kDa HLA class I heavy chain in response to IFN-gamma or TNF in a time- and dose-dependent fashion, and a synergism between IFN-gamma and TNF was observed. Immunoprecipitation of IFN-gamma- or TNF-induced FS-4 cell culture supernatants by mAb A1.4 revealed an additional 33-kDa protein in association with the 37-kDa heavy chain. The 33-kDa protein appeared to be expressed in a 38-kDa form on the membrane of FS-4 cells induced by IFN-gamma or TNF, as A1.4 immunoprecipitated the 38-kDa band in association with the 44-kDa transmembrane HLA class I heavy chain. Release of the 37-kDa heavy chain could well be due to an alternative RNA splicing with the deletion of exon 5 encoding the hydrophobic transmembrane region of membrane-anchored HLA class I heavy chain. Northern blot analysis and S1 nuclease protection assay suggested the existence of HLA class I heavy chain mRNA lacking exon 5 in IFN-gamma- or TNF-induced FS-4 cells. Southern blot analysis on the products of reverse transcription-polymerase chain reaction amplification from cytoplasmic RNA confirmed induction of alternative splicing by these cytokines. Our results suggest that cytokine-induced production of soluble HLA class I molecules may play important roles in the regulation of T cell interaction with antigen-presenting cells.
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Department of Microbiology, New York University School of Medicine, New York 10016, USA.
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D017398:Alternative Splicing / Q000235:genetics*; D001345:Autoradiography; D001483:Base Sequence; D015152:Blotting, Northern; D015139:Blotting, Southern; D002478:Cells, Cultured; D004591:Electrophoresis, Polyacrylamide Gel; D005347:Fibroblasts / Q000276:immunology; D006680:HLA Antigens / Q000096:biosynthesis / Q000235:genetics* / Q000276:immunology; D015395:Histocompatibility Antigens Class I / Q000096:biosynthesis / Q000235:genetics* / Q000276:immunology; D006801:Humans; D007371:Interferon-gamma / Q000502:physiology*; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction; D011233:Precipitin Tests; D014409:Tumor Necrosis Factor-alpha / Q000502:physiology*
D006680:HLA Antigens; D015395:Histocompatibility Antigens Class I; D014409:Tumor Necrosis Factor-alpha; D007371:Interferon-gamma