A major role of PKC θ and NFκB in the regulation of hTERT in human T lymphocytes

Expression of the telomerase catalytic subunit (TERT) is the rate-limiting determinant of telomerase activity in most human cells. In this work, we examined the participation of protein kinase C (PKC) in the regulation of hTERT expression in human T lymphocytes. Transient expression assays using luciferase reporter plasmids containing hTERT promoter showed that overexpression of PKC θ, but not the other PKC isoforms, could activate the promoter activity of hTERT in resting T lymphocytes. Among the PKC θ-activated signalings, we presented evidence that the expression of hTERT is mediated through NFκB but not through MEK or c-Jun N-terminal kinase pathways. Analysis of the hTERT promoter occupancy in vivo using chromatin immunoprecipitation assays, however, did not detect an increased binding of NFκB to the hTERT promoter in the activated T cells, although an increased binding of cMyc and Sp1 was detected. Together with the observation that inhibition of NFκB eliminated the induction of cMyc in activated T cells, these results suggest that PKC θ-activated NFκB signaling regulates the expression of hTERT via cMyc in human T lymphocytes.