title: 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.
authors.affiliation: Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, Singapore.
authors.forename: Dashayini
authors.initials: D
authors.lastname: Mahalingam
authors.forename: Ling L
authors.initials: LL
authors.lastname: Tay
authors.forename: Wei H
authors.initials: WH
authors.lastname: Tan
authors.forename: Juin H
authors.initials: JH
authors.lastname: Chai
authors.forename: Xueying
authors.initials: X
authors.lastname: Wang
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D064007:Ataxia Telangiectasia Mutated Proteins; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D049109:Cell Proliferation; D002478:Cells, Cultured; D004249:DNA Damage; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D005347:Fibroblasts / Q000166:cytology / Q000502:physiology; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism; D046228:Microarray Analysis; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D012313:RNA / Q000235:genetics* / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology; D019098:Telomerase / Q000235:genetics / Q000378:metabolism*; D016615:Telomere / Q000378:metabolism; D035341:Telomeric Repeat Binding Protein 2 / Q000235:genetics / Q000378:metabolism*; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism; D025521:Tumor Suppressor Proteins / Q000235:genetics / Q000378:metabolism*; D000097642:GADD45 Proteins
chemical_list: D064007:Ataxia Telangiectasia Mutated Proteins; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D047908:Intracellular Signaling Peptides and Proteins; D017346:Protein Serine-Threonine Kinases; D012313:RNA; D019098:Telomerase; D035341:Telomeric Repeat Binding Protein 2; D016159:Tumor Suppressor Protein p53; D025521:Tumor Suppressor Proteins; D000097642:GADD45 Proteins; C504753:TERF2 protein, human; C422952:telomerase RNA; C576324:ATM protein, human