CsA-sensitive purine-box transcriptional regulator in bronchial epithelialcells contains NF45, NF90, and Ku

Human bronchial epithelial (HBE) cells express interleukin (IL)-2 [Y.Aoki, D. Qiu, A. Uyei, and P. N. Kao. Am. J. Physiol. 272 (Lung Cell. Mol. Physio l. 16): L276-L286, 1997]. 16HBE-transformed cells contain constitutive and inducible nuclear DNA-binding activity for the purine-box/nuclear factor (N F) of activated T cell (NFAT) target DNA sequence in the human IL-2 enhance r. Transcriptional activation through the purine-box DNA sequence requires stimulation with phorbol 12-myristate 13-acetate + ionomycin, and this acti vation is inhibited by cyclosporin A. Immunohistochemical staining of 16HBE cells demonstrates nuclear expression of the purine-box DNA-binding protei ns NF45 and NF90 and no expression of NFATp or NFATc. NF90 and NF45 associa te with the DNA-dependent protein kinase catalytic subunit and the DNA-targ eting subunits Ku80 and Ku70 (N. S. Ting, P. N. Kao, D. W. Chan, L. G. Lint ott, and S. P. Lees-Miller. J. Biol. Chem. 273. 2136-2145, 1998). Antibodie s to Ku potently inhibit the purine-box DNA-binding complex. The purine-box transcriptional regulator in 16HBE cells likely comprises NF45, NF90, Ku80 , Ku70, and the DNA-dependent protein kinase catalytic subunit.