scholarly journals Human Telomerase Expression is under Direct Transcriptional Control of the Telomere-binding-factor TRF2

2020 ◽  
Author(s):  
Shalu Sharma ◽  
Ananda Kishore Mukherjee ◽  
Shuvra Shekhar Roy ◽  
Sulochana Bagri ◽  
Silje Lier ◽  
...  
Keyword(s):  
Cancer Cells ◽  
Transcriptional Control ◽  
Transcriptional Start Site ◽  
Telomerase Activity ◽  
Dependent Manner ◽  
Telomere Binding Protein ◽  
G Quadruplex ◽  
Underlying Mechanisms ◽  
Human Telomerase ◽  
Promoter Mutations

AbstractTight regulatory mechanisms to maintain repression of human Telomerase (hTERT), the sole protein that synthesizes telomeres, is crucial for normal adult somatic cells. In contrast, enhanced telomerase activity and resulting pathological maintenance of telomeres, is widely understood as causal in >90% of human cancers. These implicate underlying mechanisms connecting hTERT regulation and telomeres, possibly through telomeric proteins, that remain unclear. In light of of recent work by us and others showing non-telomeric function of the telomere-binding protein TRF2, here we examined whether and how TRF2 affected hTERT regulation. Direct binding of TRF2 – spanning ∼450 bp of the hTERT promoter from the Transcriptional Start Site (TSS) – led to TRF2-dependent recruitment of the polycomb repressor complex PRC2 in both normal and cancer cells. This induced repressor histone modifications resulting in TRF2-dependent hTERT repression. Mutations in the hTERT promoter, found frequently in aggressive glioblastoma and reported to destabilize the G-quadruplex structure, resulted in loss of TRF2 binding and consequent hTERT over-expression. Conversely, using G-quadruplex-stabilizing ligands we regained TRF2 binding, hTERT re-suppression, in highly proliferating glioblastoma cells with telomerase hyperactivation due to hTERT promoter mutations. Together, results herein demonstrate direct control of hTERT through TRF2 in a G-quadruplex-dependent manner – implicating mechanisms of how telomerase regulation might be linked to telomeres in normal and cancer cells.

scholarly journals The human telomerase 'Insertion in Fingers Domain' can mediate enzyme processivity and telomerase recruitment to telomeres in a TPP1-dependent manner

2015 ◽  
pp. MCB.00746-15 ◽  
Author(s):  
Tsz Wai Chu ◽  
Yasmin D'Souza ◽  
Chantal Autexier
Keyword(s):  
Cell Survival ◽  
Human Cancer ◽  
Telomerase Activity ◽  
Dependent Manner ◽  
Human Cancer Cells ◽  
Growth Defects ◽  
Telomere Binding Protein ◽  
Telomere Association ◽  
Human Telomerase ◽  
Reduced Activity

In most human cancer cells, cellular immortalization relies on the activation and recruitment of telomerase to telomeres. The telomere binding protein, TPP1, and the TEN domain of the telomerase catalytic subunit, TERT, regulate telomerase recruitment. TERT contains a unique ‘insertion in fingers domain' (IFD) located within the conserved reverse transcriptase domain. We report the role of specific hTERT IFD residues in the regulation of telomerase activity and processivity, recruitment to telomeres and cell survival. One hTERT IFD variant, hTERT-L805A, with reduced activity and processivity, showed impaired telomere association, which could be partially rescued by overexpression of TPP1-POT1. Another previously reported hTERT IFD mutant enzyme with similarly low levels of activity and processivity, hTERT-V791Y, displayed defects in telomere binding and was insensitive to TPP1-POT1 overexpression. Our results provide the first evidence that the IFD can mediate enzyme processivity and telomerase recruitment to telomeres in a TPP1-dependent manner. Moreover, unlike hTERT-V791Y, hTERT-V763S, a variant with reduced activity but increased processivity, and hTERT-L805A, could both immortalize limited lifespan cells, but cells expressing these two mutant enzymes displayed growth defects, increased apoptosis, DNA damage at telomeres and short telomeres. Our results highlight the importance of the IFD in maintaining short telomeres, and cell survival.

Mechanism of Cepharanthine Cytotoxicity in Human Ovarian Cancer Cells

Planta Medica ◽  
2018 ◽  
Vol 85 (01) ◽  
pp. 41-47 ◽  
Author(s):  
Vilawan Payon ◽  
Chanaporn Kongsaden ◽  
Wannarasmi Ketchart ◽  
Apiwat Mutirangura ◽  
Piyanuch Wonganan
Keyword(s):  
Ovarian Cancer ◽  
Cancer Cells ◽  
Ovarian Cancer Cell ◽  
Apoptotic Cell ◽  
Chemotherapeutic Agents ◽  
Ovarian Cancer Cells ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Ovarian Cancer Cell Lines ◽  
Underlying Mechanisms

AbstractCepharanthine (CEP), a medicinal product derived from Stephania cephalantha Hayata, possesses a potent cytotoxicity against several types of cancers. Recently, we have found that CEP could efficiently inhibit the growth of mutated p53 colon cancer cells, which are often resistant to commonly used chemotherapeutic agents. In this study, we evaluated the cytotoxic effect and the underlying mechanisms of CEP on both chemosensitive CaOV-3 and chemoresistant OVCAR-3 ovarian cancer cell lines. The present study demonstrated that CEP significantly inhibited the growth of CaOV-3 and OVCAR-3 cells in a time- and concentration-dependent manner. CEP arrested CaOV-3 and OVCAR-3 cells in the G1 phase and S phase of cell cycle, respectively. Western blot analysis demonstrated that CEP markedly increased the expression of p21Waf1 protein and decreased the expression of cyclins A and D proteins in both CaOV-3 and OVCAR-3 cells. Additionally, CEP triggered apoptotic cell death in OVCAR-3 cells. Taken together, the above results suggest that CEP is a promising anticancer drug for ovarian cancer.

Anti-Proliferative and Anti-Telomerase Effects of Blackberry Juice and Berry-Derived Polyphenols on HepG2 Liver Cancer Cells and Normal Human Blood Mononuclear Cells

2021 ◽  
Vol 21 ◽  
Author(s):  
Delaram Moghadam ◽  
Reza Zarei ◽  
Mohsen Tatar ◽  
Zahra Khoshdel ◽  
Farideh Jalali Mashayekhi ◽  
...  
Keyword(s):  
Cancer Cells ◽  
Gallic Acid ◽  
Hepg2 Cells ◽  
Mononuclear Cells ◽  
Telomerase Activity ◽  
Anthocyanin Content ◽  
Dependent Manner ◽  
Normal Peripheral Blood ◽  
Significant Difference ◽  
Blood Mononuclear Cells

Background: Previous studies have provided strong evidence for anticancer activity of berry fruits. Objective: In this study, we investigated the effects of blackberry juice and three berry- polyphenolic compounds on cell proliferation and telomerase activity in human hepatoma HepG2 and normal peripheral blood mononuclear cells (PBMCs). Methods: The cell viability and telomerase activity were measured by MTT and TRAP assay, respectively. Berry effects on the expression of genes were determined by quantitative RT-PCR assay. Results: Blackberry, gallic acid, and resveratrol inhibited proliferation of both HepG2 and PBMC cells in a dose-dependent manner. Resveratrol was more effective than gallic acid for reducing the viability of HepG2 cells, but both showed the same level of growth inhibition in PBMC cells. Berry, resveratrol, and gallic acid significantly inhibited telomerase activity in HepG2 cells. The antiproliferative effect of berry was associated with apoptotic DNA fragmentation. Gallic acid was more effective for reducing telomerase activity than resveratrol, but anthocyanin moderately increased telomerase activity in cancer cells. Telomerase activity was induced by all three polyphenols in PBMCs. Overall, Krumanin chloride was more effective to induce telomerase than gallic acid and resveratrol in PBMC cells. There was no significant difference in hTERT, hTR, and Dnmts expressions between berry treated and the control untreated HepG2 cells. But, a significant downregulation of HDAC1 and HDAC2 and upregulation of SIRT1 were observed in berry-treated cells. Conclusion : These data indicate that the berry anticancer effect is associated with antitelomerase activity and changes in HDACs expression. The data also suggest that berry antitelomerase activity is mainly related to its gallic acid and resveratrol, but not anthocyanin content.

scholarly journals Putative Telomere-Recruiting Domain in the Catalytic Subunit of Human Telomerase

2003 ◽  
Vol 23 (9) ◽  
pp. 3237-3246 ◽  
Author(s):  
Blaine N. Armbruster ◽  
Katherine T. Etheridge ◽  
Dominique Broccoli ◽  
Christopher M. Counter
Keyword(s):  
Catalytic Activity ◽  
Cancer Cells ◽  
Catalytic Subunit ◽  
Telomere Elongation ◽  
Telomere Binding Protein ◽  
Cell Immortalization ◽  
Higher Eukaryotes ◽  
Human Telomerase

ABSTRACT Telomerase, the enzyme that elongates telomeres, is essential to maintain telomere length and to immortalize most cancer cells. However, little is known about the regulation of this enzyme in higher eukaryotes. We previously described a domain in the hTERT telomerase catalytic subunit that is essential for telomere elongation and cell immortalization in vivo but dispensable for catalytic activity in vitro. Here, we show that fusions of hTERT containing different mutations in this domain to the telomere binding protein hTRF2 redirected the mutated hTERT to telomeres and rescued its in vivo functions. We suggest that this domain posttranscriptionally regulates telomerase function by targeting the enzyme to telomeres.

scholarly journals hTERT Downregulation Attenuates Resistance to DOX, Impairs FAK-Mediated Adhesion, and Leads to Autophagy Induction in Breast Cancer Cells

Cells ◽  
2021 ◽  
Vol 10 (4) ◽  
pp. 867
Author(s):  
Aleksandra Romaniuk-Drapała ◽  
Ewa Totoń ◽  
Natalia Konieczna ◽  
Marta Machnik ◽  
Wojciech Barczak ◽  
...  
Keyword(s):  
Breast Cancer ◽  
Cancer Cells ◽  
Breast Cancer Cells ◽  
Therapeutic Potential ◽  
Telomerase Activity ◽  
Telomere Maintenance ◽  
Population Doubling ◽  
Cell Cycle Distribution ◽  
Human Telomerase Reverse Transcriptase ◽  
Human Telomerase

Telomerase is known to contribute to telomere maintenance and to provide cancer cell immortality. However, numerous reports are showing that the function of the enzyme goes far beyond chromosome ends. The study aimed to explore how telomerase downregulation in MCF7 and MDA-MB-231 breast cancer cells affects their ability to survive. Consequently, sensitivity to drug resistance, proliferation, and adhesion were assessed. The lentiviral-mediated human telomerase reverse transcriptase (hTERT) downregulation efficiency was performed at gene expression and protein level using qPCR and Western blot, respectively. Telomerase activity was evaluated using the Telomeric Repeat Amplification Protocol (TRAP) assay. The study revealed that hTERT downregulation led to an increased sensitivity of breast cancer cells to doxorubicin which was demonstrated in MTT and clonogenic assays. During a long-term doubling time assessment, a decreased population doubling level was observed. Interestingly, it did not dramatically affect cell cycle distribution. hTERT downregulation was accompanied by an alteration in β1-integrin- and by focal adhesion kinase (FAK)-driven pathways together with the reduction of target proteins phosphorylation, i.e., paxillin and c-Src. Additionally, autophagy activation was observed in MDA-MB-231 cells manifested by alternations in Atg5, Beclin 1, LC3II/I ratio, and p62. These results provide new evidence supporting the possible therapeutic potential of telomerase downregulation leading to induction of autophagy and cancer cells elimination.

scholarly journals Efficient inhibition of human telomerase activity by antisense oligonucleotides sensitizes cancer cells to radiotherapy

2006 ◽  
Vol 27 (9) ◽  
pp. 1185-1191 ◽  
Author(s):  
Xue-mei JI ◽  
Cong-hua XIE ◽  
Ming-hao FANG ◽  
Fu-xiang ZHOU ◽  
Wen-jie ZHANG ◽  
...  
Keyword(s):  
Cancer Cells ◽  
Antisense Oligonucleotides ◽  
Telomerase Activity ◽  
Human Telomerase

Selective Apoptosis and Growth Impairment of Cancer Cells Induced by Human Telomerase Reverse Transcriptase (hTERT) Targeting Artificial MicroRNA

2021 ◽  
Vol 13 (9) ◽  
pp. 1644-1656
Author(s):  
Hongjun Lin ◽  
Pengliang Xin ◽  
Huangen Li ◽  
Mingqing Tang
Keyword(s):  
Reverse Transcriptase ◽  
Cancer Cells ◽  
Telomerase Activity ◽  
Telomerase Reverse Transcriptase ◽  
Human Telomerase Reverse Transcriptase ◽  
Reverse Transcription Pcr ◽  
Angiogenesis Assay ◽  
Amplification Protocol ◽  
Huvec Cells ◽  
Human Telomerase

Human telomerase reverse transcriptase (hTERT) is a promising cancer target, and amiRNA particle displays the siRNA’s specificity and miRNA’s safety, suggesting that cancers can be treated more effective and safely by hTERT targeting amiRNA particles. Hela, NCI-H446, U2-OS and Huvec cells were transfected by hTERT targeting amiRNA particles. hTERT expression, telomerase activity and cell viability were evaluated by quantitative reverse transcription-PCR (qRT-PCR), western blot (WB), telomeric repeat amplification protocol (TRAP) assays, MTT method, transwell protocol, fluorescence-activated cell sorting (FACS) technologies, angiogenesis assay, and xenograft tumor models. Results: hTERT expression and telomerase activity in Hela and NCIH446 were significantly inhibited by amiRNA. Anti-proliferation and pro-apoptosis effects were only observed in transfected Hela and NCI-H446 cells, but anti-migration and anti-angiogenesis effects were presented in transfected Huvec cells. More interestingly, low to 1.56 nM amiRNA can inhibit the proliferation of Hela cells by 80.99±5.24%. Conclusion: amiRNA selectively and effectively impairs the growth, and assists the apoptosis of telomerase-positive cancer cells.

scholarly journals Cancer-associated TERT promoter mutations abrogate telomerase silencing

eLife ◽  
2015 ◽  
Vol 4 ◽  
Author(s):  
Kunitoshi Chiba ◽  
Joshua Z Johnson ◽  
Jacob M Vogan ◽  
Tina Wagner ◽  
John M Boyle ◽  
...  
Keyword(s):  
Stem Cells ◽  
Embryonic Stem ◽  
Telomerase Activity ◽  
Human Telomerase Reverse Transcriptase ◽  
Telomere Shortening ◽  
Tert Promoter ◽  
Tert Promoter Mutations ◽  
Human Telomerase ◽  
Promoter Mutations ◽  
Additional Tumor

Mutations in the human telomerase reverse transcriptase (TERT) promoter are the most frequent non-coding mutations in cancer, but their molecular mechanism in tumorigenesis has not been established. We used genome editing of human pluripotent stem cells with physiological telomerase expression to elucidate the mechanism by which these mutations contribute to human disease. Surprisingly, telomerase-expressing embryonic stem cells engineered to carry any of the three most frequent TERT promoter mutations showed only a modest increase in TERT transcription with no impact on telomerase activity. However, upon differentiation into somatic cells, which normally silence telomerase, cells with TERT promoter mutations failed to silence TERT expression, resulting in increased telomerase activity and aberrantly long telomeres. Thus, TERT promoter mutations are sufficient to overcome the proliferative barrier imposed by telomere shortening without additional tumor-selected mutations. These data establish that TERT promoter mutations can promote immortalization and tumorigenesis of incipient cancer cells.

Epigallocatechin-3-gallate inhibits proliferation and triggers apoptosis in colon cancer via the hedgehog/phosphoinositide 3-kinase pathways

2021 ◽  
Author(s):  
Feng Ding ◽  
Su Yang
Keyword(s):  
Colon Cancer ◽  
Tumor Growth ◽  
Cancer Cells ◽  
Nude Mice ◽  
The Body ◽  
Antiproliferative Effect ◽  
Migration And Invasion ◽  
Dependent Manner ◽  
Colon Cancer Cells ◽  
Underlying Mechanisms

The present study evaluated whether EGCG effectively attenuates tumor growth in colon cancer cells and in the xenografts of nude mice and to investigated the underlying mechanisms by focusing on the Shh and PI3K pathways. Three kinds of colon cancer cells and BALB/c nude mice were used to evaluate the antiproliferative effect of EGCG.The results showed that EGCG exhibited an antiproliferative effect against colon cancer cells in a dose-dependent manner with low toxicity against normal colon epithelial cells. Administration of EGCG caused significant apoptosis and inhibited the migration and invasion of colon cancer cells. The toxic effect of EGCG was accompanied by downregulation of the Shh and PI3K/Akt pathways. In addition, EGCG reduced tumor weight without affecting the body weight of nude mice and inhibited the activation of the Shh and PI3K/Akt pathways in tumor tissue. Purmorphamine (Shh agonist) or IGF-1 (PI3K agonist) partly abolished the effect of EGCG on cell proliferation, migration and apoptosis. Cyclopamine (Shh inhibitor) and LY294002 (PI3K inhibitor) showed the similar toxic effects as EGCG on colon cancer cells. In conclusion, EGCG inhibited colon tumor growth via downregulation of the Shh and PI3K pathways and may be a potential chemotherapeutic agent against colon cancer.

Sign in / Sign up

Export Citation Format

Share Document