title: NF-kappa B regulates expression of the MHC class I-related chain A gene in activated T lymphocytes.
abstract: MHC class I-related chain A gene (MICA) is a stress-regulated, HLA-related molecule which exhibits a restricted pattern of expression. MICA protein is up-regulated on different tumor cells, and is recognized by the lectin-like NKG2D molecule expressed by cytotoxic gammadelta T lymphocytes, CD8+ alphabeta T lymphocytes, and NK cells. Although MICA is not expressed on resting lymphocytes, we demonstrated that it is induced on activated T cells. Because NF-kappaB is actively involved in T cell activation, and is constitutively activated in many tumors, here we investigated whether NF-kappaB may modulate MICA expression. Treatment with the NF-kappaB inhibitor sulfasalazine (Sz) resulted in a dose-dependent inhibition of MICA expression in anti-CD3- and anti-CD28/PMA-activated T lymphocytes, as assessed by Western blot and RT-PCR analysis. Moreover, Sz also down-regulated MICA expression on epithelial tumor HeLa cells. MICA expression was accompanied by a Sz-sensitive IkappaBalpha degradation. EMSA with nuclear extracts from anti-CD3- and anti-CD28/PMA-stimulated T lymphocytes demonstrated the binding of a potential NF-kappaB family transcription factor to a MICA gene intron 1-derived oligonucleotide that contains a putative kappaB binding site. Supershift assays demonstrated the presence of p65(RelA)/p50 heterodimers and p50/p50 homodimers in the NF-kappaB complexes bound to the kappaB-MICA oligonucleotide. Transient transfection of HeLa cells with p65(RelA) up-regulated MICA expression, as assessed by Western blot and flow cytometry analysis. Hence, we conclude that NF-kappaB regulates MICA expression on activated T lymphocytes and HeLa tumor cells, by binding to a specific sequence in the long intron 1 of the MICA gene. This constitutes the first description of a transcription factor that regulates MICA gene expression.
authors.affiliation: Laboratorio de Inmunogenética, Hospital de Clínicas "José de San Martín", and Departamento de Microbiología, Facultad de Medicina, Universidad de Buenos Aires (UBA), Argentina.
authors.forename: Luciana L
authors.initials: LL
authors.lastname: Molinero
authors.forename: Mercedes B
authors.initials: MB
authors.lastname: Fuertes
authors.forename: María Victoria
authors.initials: MV
authors.lastname: Girart
authors.forename: Leonardo
authors.initials: L
authors.lastname: Fainboim
authors.forename: Gabriel A
authors.initials: GA
authors.lastname: Rabinovich
authors.forename: Mónica A
authors.initials: MA
authors.lastname: Costas
authors.forename: Norberto W
authors.initials: NW
authors.lastname: Zwirner
mesh_terms: D000911:Antibodies, Monoclonal / Q000494:pharmacology; D018106:CD28 Antigens / Q000276:immunology; D017252:CD3 Complex / Q000276:immunology; D002478:Cells, Cultured; D015536:Down-Regulation / Q000187:drug effects / Q000276:immunology; D024202:Electrophoretic Mobility Shift Assay; D005786:Gene Expression Regulation / Q000276:immunology*; D006367:HeLa Cells; D015395:Histocompatibility Antigens Class I / Q000096:biosynthesis* / Q000235:genetics*; D006801:Humans; D007438:Introns / Q000235:genetics; D008213:Lymphocyte Activation / Q000187:drug effects / Q000235:genetics*; D016328:NF-kappa B / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000502:physiology*; D011485:Protein Binding / Q000235:genetics / Q000276:immunology; D012460:Sulfasalazine / Q000494:pharmacology; D016176:T-Lymphocyte Subsets / Q000187:drug effects / Q000276:immunology* / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014162:Transfection
chemical_list: D000911:Antibodies, Monoclonal; D018106:CD28 Antigens; D017252:CD3 Complex; D015395:Histocompatibility Antigens Class I; C099187:MHC class I-related chain A; D016328:NF-kappa B; D012460:Sulfasalazine; D013755:Tetradecanoylphorbol Acetate