Mutant telomerase RNAs induce DNA damage and apoptosis via the TRF2-ATM pathway in telomerase-overexpressing primary fibroblasts

Abstract

Mutant template human telomerase RNAs (MT-hTers) have been shown to induce apoptosis in various cancer cells with high telomerase activity. However, the mechanism by which MT-hTers inhibit the growth of cancer cells and their effects on normal cells remain unknown. To determine the effects of MT-hTers on normal cells, MT-hTer-47A and -AU5 were introduced into IMR90 lung fibroblasts, which have low telomerase levels. Growth of IMR90 cells after MT-hTers infection was not significantly impaired; however, similar treatments in telomerase- overexpressing IMR90 [IMR90 wild-type (WT)hTERT] cells inhibited cell proliferation and induced apoptosis. Confocal microscopy showed that MT-hTers induced DNA damage foci (i.e. 53BP1 and γ-H2AX) in IMR90 WThTERT cells. Microarray analysis revealed that GADD45γ was significantly elevated in MT-hTer-treated IMR90 WThTERT cells. MT-hTers also induced ATM phosphorylation at Ser1981 in IMR90 WThTERT cells, and western blot analysis revealed high levels of phosphorylated p53 after the down-regulation of cellular TRF2 expression in MT-hTer-treated IMR90 WThTERT cells. Taken together, we have shown that MT-hTers induce double-stranded DNA break-like damages in telomerase positive IMR90 WThTERT cells after phosphorylation of ATM and p53 via suppression of TRF2, which may eventually lead to apoptosis via elevation of GADD45γ. Structured digital abstract and by) and by) We identified that mutant template human telomerase RNAs (MT-hTers) induce double strand breaks (DSBs)-like damages following 53BP1 and γ-H2AX foci formation in telomerase-overexpressing IMR90 (IMR90 WThTERT) cells, but not in normal IMR90 cells under similar treatments. Western blot analysis showed that these effects were mediated via the TRF2-ATM pathway and p53 activation, ultimately leading to apoptosis plausibly following elevation of GADD45γ. © 2011 FEBS.