Mutated telomeres sensitize tumor cells to anticancer drugs independently of telomere shortening and mechanisms of telomere maintenance

Cerone, Maria Antonietta; Londoño-Vallejo, J. Arturo; Autexier, Chantal

doi:10.1038/sj.onc.1209727

Cited by 27 publications

(31 citation statements)

References 44 publications

(59 reference statements)

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“…Upon drug treatment, these cells showed a significant reduction in proliferative potential and revealed an increase in telomere length heterogeneity, even though the overall length of telomeres was maintained with no signal-free ends or chromosomal fusions, suggesting that the incorporated mutant repeats interfere with telomere structure maintenance and heighten tumor cells to harmful stimuli. 45 A similar process may occur in patients when only a single hTERC template is mutated. It is known that some proportion of patients with heterozygote telomerase allele would be at risk of exhausting the regenerative capacity of their marrow stem cells during adulthood, especially when challenged by environmental insults.…”

Section: Discussionmentioning

confidence: 99%

“…Recently, Cerone and colleagues have demonstrated that a mutant template hTERC RNA can dictate the synthesis of aberrant telomeric repeats onto chromosome ends of human breast cancer cell lines with long overall telomeres. 45 Cells with the mutant repeats appeared to be more sensitive to anticancer drugs etoposide and doxorubicin. Upon drug treatment, these cells showed a significant reduction in proliferative potential and revealed an increase in telomere length heterogeneity, even though the overall length of telomeres was maintained with no signal-free ends or chromosomal fusions, suggesting that the incorporated mutant repeats interfere with telomere structure maintenance and heighten tumor cells to harmful stimuli.…”

Section: Discussionmentioning

confidence: 99%

“…When the A48G RNA variant was transcribed in vitro and used to assemble with the hTERT protein expressed in an RRL, irregular telomeric repeats appeared to be synthesized ( Figure 4A, lane 40); these unusual repeats, however, were not produced by complexes with either the wild-type hTERC (lanes [46][47] or other hTERC RNA variants (G58A or ⌬28-34, lanes [42][43][44][45]. These data prompted experiments to determine if any of these RNA sequence changes inhibited the normal level of telomerase enzymatic function in a dominant-negative fashion, as had been observed for some genetically engineered RNA template mutations.…”

Section: Hterc Template Mutations Seem To Act As Dominant Negatives Amentioning

confidence: 99%

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Functional characterization of natural telomerase mutations found in patients with hematologic disorders

Xin

Beauchamp

Calado

et al. 2006

Blood

105

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Human telomerase hTERC RNA serves as a template for the catalytic hTERT protein to synthesize telomere repeats at chromosome ends. We have recently shown that some patients with bone marrow failure syndromes are heterozygous carriers for hTERC or hTERT mutations. These sequence variations usually lead to a compromised telomerase function by haploinsufficiency. Here, we provide functional characterization of an additional 8 dis- IntroductionTelomerase is a specialized reverse transcriptase (RT) that adds long, repetitive stretches of simple telomeric DNA sequence (ie, TTAGGG in the vertebrates) onto chromosomal termini. 1 This cellular RT protein (TERT) copies a short stretch of nucleotides located within the template region of an integral RNA component (TERC) into telomeric DNA repeats. 1 Vertebrate TERCs are believed to adopt a complex, folded secondary structure 2 as depicted for human TERC (hTERC) in Figure 1A. We have recently conducted extensive site-directed mutagenesis analysis of hTERC to show that much of the structure folded as predicted. 3 As is true of many biologically active RNA molecules, most of the internally base-paired regions of hTERC can be extensively mutated without loss of function, provided that the normal base-pairing pattern is preserved. 3 However, at certain locations, especially of the single-stranded template region that is copied into telomeric DNA, specific RNA base sequences have been shown to be required for biologic activity. 4 Telomerase catalytic proteins (TERTs) from evolutionary distant organisms share a conserved structural organization that can be divided into 3 functional domains ( Figure 1C). 5 The telomerasespecific domains exist at both the N and C termini of TERTs that are not present in any of the viral RTs. 6 The N-terminal region is required to participate in enzymatic function, 7,8 in assembly of the protein with its integral hTERC RNA component,7,9 and in the homodimerization of the protein (ie, hTERT protein-protein interaction), 7,9,10 whereas the C-terminal domain is required for telomerase-specific activity other than its catalytic function 11,12 as well as in the telomeric nucleotide addition processivity process. [13][14][15] The functional RT domain with the universally conserved RT motifs is almost centrally located in the protein primary sequence ( Figure 1C). The fact that mutations of key residues that are known to affect its conventional RT catalytic activity also negatively influence telomerase activity strongly argues that telomerase RT domain is the catalytic domain of the enzyme complex. 13,[15][16][17][18] Inherited mutations in both hTERC RNA and hTERT protein underlie rare bone marrow failure syndromes, autosomal dominant dyskeratosis congenita (DC) and acquired aplastic anemia (AA). [19][20][21] DC is characterized by abnormal skin pigmentation, nail dystrophy, and oral leukoplakia and is often complicated by life-threatening bone marrow failure and immunodeficiency. 22 Lymphocytes from patients show decreased hTERC expression, decreased t...

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Hterc Template Mutations Seem To Act As Dominant Negatives Amentioning

confidence: 99%

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Functional characterization of natural telomerase mutations found in patients with hematologic disorders

Xin

Beauchamp

Calado

et al. 2006

Blood

105

View full text Add to dashboard Cite

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“…cDNA was generated from total RNA and PCR was used to detect hTERT with primers HT1 and HT5 (Bodnar et al, 1998); mTERT with mTERT-WTF (5Ј-GACATGGAGAACAAGCTGTTTGCTGAG-3Ј) and mTERTshortR (5Ј-ATCTTGTATATATTGATGCAGACTGTCTGG-3Ј) primers; hTR with hTR-F3B and hTR-R3C primers (Nakamura et al, 1997); and mTR with mTR-F2-RT (5Ј-CCTAACCCTGATTTTCATTAGCTGTGGG-3Ј) and mTR-R2-RT (5Ј-GAGGCTCGGGAACGCGCGGTGGCCC-3Ј) primers. Human and mouse GAPDH was amplified with primers RT11 and RT12 (Cerone et al, 2006).…”

Section: Rna Isolation and Rt-pcrmentioning

confidence: 99%

Telomeric function of mammalian telomerases at short telomeres

Fakhoury

Marie-Egyptienne

Londoño-Vallejo

et al. 2010

Journal of Cell Science

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SummaryTelomerase synthesizes telomeric sequences and is minimally composed of a reverse transcriptase (RT) known as TERT and an RNA known as TR. We reconstituted heterologous mouse (m) and human (h) TERT-TR complexes and chimeric mTERT-hTERT-hTR complexes in vitro and in immortalized human alternative lengthening of telomere (ALT) cells. Our data suggest that species-specific determinants of activity, processivity and telomere function map not only to the TR but also to the TERT component. The presence of hTERT-hTR, but not heterologous TERT-TR complexes or chimeric mTERT-hTERT-hTR complexes, significantly reduced the percentage of chromosomes without telomeric signals in ALT cells. Moreover, heterologous and chimeric complexes were defective in recruitment to telomeres. Our results suggest a requirement for several hTERT domains and interaction with multiple proteins for proper recruitment of telomerase to the shortest telomeres in human ALT cells. Late-passage mTERT -/-mouse embryonic stem (ES) cells ectopically expressing hTERT or mTERT harboured fewer chromosome ends without telomeric signals and end-to-end fusions than typically observed in late-passage mTERT -/-ES cells. The ability of hTERT to function at mouse telomeres and the inability of mTERT to function at human telomeres suggest that mechanisms regulating the recruitment and activity of hTERT at mouse telomeres might be less stringent than the mechanisms regulating mTERT at human telomeres.

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“…Experiments carried out using human cell lines have also established an increased sensitivity to DNA damaging agents following inhibition of telomerase (Cerone et al, 2006a, b;Saretzki, 2003). Furthermore, when telomere integrity is compromised by expressing a mutant template RNA that results in repeats unable to recruit the shelterin complex, this also results in increased sensitivity to DNA damage (Cerone et al, 2006a). Increased drug sensitivity may occur before detectable telomere shortening (Masutomi et al, 2005), raising the possibility that telomerase may provide a protective function independent of its role in maintaining telomeric DNA arrays (Martinez & Blasco, 2011).…”

Section: Tmm and Drug Sensitivitymentioning

confidence: 99%