Phorbol esters and calcium ionophores differentially regulate the transcription of gamma-T-cell antigen receptor gene in human thymocytes.

The phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA) and the calcium ionophore ionomycin differentially regulated the expression of the gamma-T-cell antigen receptor (gamma-TCR) gene in human thymocytes. Ionomycin induced an increase in gamma-TCR mRNA while TPA prevented this effect. The effects of ionomycin and TPA are completely reversed upon their removal. Protein kinase C-depleted cells are unable to respond to TPA but the induction of gamma-TCR by ionomycin was unimpaired. The regulation of gamma-TCR gene expression by TPA and ionomycin occurred at the level of gene transcription, whereas the rate of gamma-TCR mRNA degradation was unaffected by TPA or ionomycin.