CD28-mediated regulation of the c-jun promoter involves the MEF2 transcription factor in Jurkat T cells.
Within a few minutes of T-cell activation, transcription of a set of genes including c-fos and c-jun is activated. For maximal induction of c-jun, at least two major signal pathways are required. One can be triggered by T-cell receptor engagement or phorbol esters and the other by anti-CD28 engagement. The c-jun promoter region between -117 and -50 contains binding sites for the transcription factors Spl, CTF, ATF/CREB, and MEF2. In this study, we sought to map the sequences in the c-jun promoter responsible for CD28-mediated induction in activated Jurkat T cell by point mutational analysis. We found that mutation of the c-jun MEF2 site strongly reduces CD28 induction of the promoter in Jurkat T cells and that MEF2D is the major binding molecule to the c-jun MEF2 site in Jurkat T cells. Mutation of the c-jun ATF site also partially reduced CD28 induction of the promoter. In addition, pretreatment with an endolysomotropic agent NH4Cl, an acidic sphingomyelinase inhibitor, completely inhibited the activation of the c-jun promoter by anti-CD28 antibody treatment, whereas pretreatment with wortmannin, a PI3-kinase inhibitor, did not affect the induction of the c-jun promoter. These results suggest that CD28 signaling leading to the c-jun promoter involves acidic sphingomyelinase, but not PI3-kinase, to activate factors binding to the MEF2 and ATF sites.
Department of Microbiology and Immunology, Sungkyunkwan University School of Medicine, Suwon, South Korea.
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Shin
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Han
D001665:Binding Sites / Q000235:genetics; D018106:CD28 Antigens / Q000502:physiology*; D004268:DNA-Binding Proteins / Q000502:physiology*; D005786:Gene Expression Regulation / Q000276:immunology*; D016758:Genes, jun / Q000276:immunology*; D006801:Humans; D019169:Jurkat Cells / Q000276:immunology / Q000378:metabolism*; D026161:MADS Domain Proteins; D064326:MEF2 Transcription Factors; D018006:Myogenic Regulatory Factors; D019869:Phosphatidylinositol 3-Kinases / Q000502:physiology; D011401:Promoter Regions, Genetic / Q000276:immunology*; D012045:Regulatory Sequences, Nucleic Acid / Q000235:genetics; D015398:Signal Transduction / Q000276:immunology; D013108:Sphingomyelin Phosphodiesterase / Q000502:physiology; D014157:Transcription Factors / Q000502:physiology*
D018106:CD28 Antigens; D004268:DNA-Binding Proteins; D026161:MADS Domain Proteins; D064326:MEF2 Transcription Factors; C578043:MEF2D protein, human; D018006:Myogenic Regulatory Factors; D014157:Transcription Factors; D019869:Phosphatidylinositol 3-Kinases; D013108:Sphingomyelin Phosphodiesterase