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Mutated RNA component of the telomerase induces apoptosis via GADD45-γ in hTERT-overexpressing primary fibroblasts

ABSTRACT: Mutant template human telomerase RNAs (MT-hTers) have been shown to induce apoptosis in various cancerous cells that have high telomerase activity. However, the exact mechanisms by which MT-hTers inhibit the growth of cancer cells and affect normal somatic cells remain largely unknown. To determine the effects of MT-hTers on normal cells, MT-hTer-47A and -AU5 were introduced into IMR90 primary lung fibroblasts that have very low endogenous hTERT levels. Growth of IMR90 cells following MT-hTers infection was not impaired, however, cell proliferation of IMR90 wild-type hTERT (WT-hTERT) cells under MT-hTers-47A and -AU5 treatment was inhibited and increased cell death was observed. FACS analysis also showed that these cells underwent apoptosis. Confocal microscopy revealed that MT-hTers induced DNA damage foci, i.e., 53BP1 and γ-H2AX, in immortalized IMR90 WT-hTERT cells. Microarray analysis of the IMR90 WT-hTERT MT-hTer-47A and -AU5 versus IMR90 MT-hTer-47A and -AU5 revealed that GADD45-γ was significantly elevated, and this result was further confirmed following RT-PCR and real time PCR assays. Moreover, we have showed that MT-hTers induce ATM phosphorylation at Ser 1981 in IMR90 WThTERT cells, and Western analysis revealed high levels of phospho p53 expression in these cells following activation of ATM. Our results also suggest that p53-dependent apoptosis in MT-hTers-infected IMR90 WT-hTERT cells could be due to a decreased expression of TRF2. Taken together, we propose a model that MT-hTers induce DSBs-like damages and trigger programmed cell death in IMR90 WT-hTERT cells following ATM-mediated phosphorylation of p53, which in turn upregulate GADD45-γ, ultimately leading to apoptosis. MT-hTer-47A and -AU5 were introduced into IMR90 primary lung fibroblasts and immortalized IMR90 WT-hTERT cells. Through microarray analysis, gene expression of MT-hTer-infected IMR90 WT-hTERT cells were compared against MT-hTer-infected IMR90 control cells.

ORGANISM(S): Homo sapiens  

SUBMITTER: Bradley Stohr   Xueying Wang  Juin H Chai  Sherry Wang  Shang Li  Elizabeth H Blackburn  Edison T Liu  Wei H Tan  Dashayini Mahalingam 

PROVIDER: E-GEOD-24975 | ArrayExpress | 2011-05-28



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