FIG. 6.
HTLV-1 p12I-mediated activation of NFAT is sensitive to inhibition of the Ras/MAPK pathway. (A) Treatment of pME- and pME-12-transfected Jurkat T cells with U0126 results in complete abrogation of p12I-mediated NFAT activity. Only values for PMA-treated cells are shown. Values represent the means of quadruplicate samples and two independent experiments. Statistical significance was analyzed by Student's t test. (B) The expression of a dominant negative mutant of AP-1 (A-Fos) (+ column) completely abrogates the p12I-mediated induction of NFAT activity. Jurkat T cells were cotransfected with pME or pME-p12 and 10 μg of pCMV500-A-Fos or the corresponding empty vector pCMV500. Only values for PMA-treated cells are shown. Values represent the means of quadruplicate samples and two independent experiments. Statistical significance was analyzed by Student's t test. Expression of A-Fos was examined by immunoblot (inset) using a monoclonal antibody directed against the A-Fos N-terminal Flag tag. (C) A-Fos potently inhibits PMA- and ionomycin-stimulated NFAT activity. Jurkat T cells were cotransfected with pNFAT-luc and the indicated amounts of pCMV500-A-Fos and treated with PMA plus ionomycin.