NF-
B Regulates Expression of the MHC Class I-Related Chain A Gene in Activated T Lymphocytes

L.L MOLINERO ; M.B FUERTES ; M.V GIRART ; L. FAINBOIM; G.A RABINOVICH ; M.A COSTAS ; N.W ZWIRNER

JOURNAL OF IMMUNOLOGY

AMER ASSOC IMMUNOLOGISTS

Lugar: Bethesda; Año: 2004 vol. 173 p. 5583 - 5590

0022-1767

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 T lymphocytes, CD8 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-B is actively involved in T cell activation, and is constitutively activated in many tumors, here we investigated whether NF-B may modulate MICA expression. Treatment with the NF-B 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 IB degradation. EMSA with nuclear extracts from anti-CD3- and anti-CD28/PMA-stimulated T lymphocytes demonstrated the binding of a potential NF-B family transcription factor to a MICA gene intron 1-derived oligonucleotide that contains a putative B binding site. Supershift assays demonstrated the presence of p65(RelA)/p50 heterodimers and p50/p50 homodimers in the NF-B complexes bound to the B-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-B 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.