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1.
Nucleic Acids Res ; 48(18): 10125-10141, 2020 10 09.
Artigo em Inglês | MEDLINE | ID: mdl-32976590

RESUMO

G-quadruplexes (G4s) are nucleic acid structure motifs that are of significance in chemistry and biology. The function of G4s is often governed by their interaction with G4-binding proteins. Few categories of G4-specific tools have been developed to inhibit G4-protein interactions; however, until now there is no aptamer tool being developed to do so. Herein, we present a novel L-RNA aptamer that can generally bind to D-RNA G-quadruplex (rG4) structure, and interfere with rG4-protein interaction. Using hTERC rG4 as the target for in vitro selection, we report the shortest L-aptamer being developed so far, with only 25 nucleotides. Notably, this new aptamer, L-Apt.4-1c, adopts a stem-loop structure with the loop folding into an rG4 motif with two G-quartet, demonstrates preferential binding toward rG4s over non-G4s and DNA G-quadruplexes (dG4s), and suppresses hTERC rG4-nucleolin interactions. We also show that inhibition of rG4-protein interaction using L-RNA aptamer L-Apt.4-1c is comparable to or better than G4-specific ligands such as carboxypyridostatin and QUMA-1 respectively, highlighting that our approach and findings expand the current G4 toolbox, and open a new avenue for diverse applications.


Assuntos
Aptâmeros de Nucleotídeos/química , Aptâmeros de Nucleotídeos/metabolismo , Quadruplex G , Fosfoproteínas/metabolismo , Proteínas de Ligação a RNA/metabolismo , RNA , Telomerase , Aptâmeros de Nucleotídeos/síntese química , Humanos , Ligação Proteica , RNA/química , RNA/metabolismo , Telomerase/química , Telomerase/metabolismo
2.
Life Sci ; 259: 118387, 2020 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-32890603

RESUMO

Telomerase is a nucleoprotein reverse transcriptase that maintains the telomere, a protective structure at the ends of the chromosome, and is active in cancer cells, stem cells, and fetal cells. Telomerase immortalizes cancer cells and induces unlimited cell division by preventing telomere shortening. Immortalized cancer cells have unlimited proliferative potential due to telomerase activity that causes tumorigenesis and malignancy. Therefore, telomerase can be a lucrative anti-cancer target. The regulation of catalytic subunit of telomerase (TERT) determines the extent of telomerase activity. miRNAs, as an endogenous regulator of gene expression, can control telomerase activity by targeting TERT mRNA. miRNAs that have a decreasing effect on TERT translation mediate modulation of telomerase activity in cancer cells by binding to TERT mRNA and regulating TERT translation. In this review, we provide an update on miRNAs that influence telomerase activity by regulation of TERT translation.


Assuntos
MicroRNAs/metabolismo , Neoplasias/enzimologia , Telomerase/metabolismo , Animais , Regulação Neoplásica da Expressão Gênica , Humanos , Neoplasias/metabolismo
3.
Nat Commun ; 11(1): 4766, 2020 09 21.
Artigo em Inglês | MEDLINE | ID: mdl-32958778

RESUMO

Germline telomere maintenance defects are associated with an increased incidence of inflammatory diseases in humans, yet whether and how telomere dysfunction causes inflammation are not known. Here, we show that telomere dysfunction drives pATM/c-ABL-mediated activation of the YAP1 transcription factor, up-regulating the major pro-inflammatory factor, pro-IL-18. The colonic microbiome stimulates cytosolic receptors activating caspase-1 which cleaves pro-IL-18 into mature IL-18, leading to recruitment of interferon (IFN)-γ-secreting T cells and intestinal inflammation. Correspondingly, patients with germline telomere maintenance defects exhibit DNA damage (γH2AX) signaling together with elevated YAP1 and IL-18 expression. In mice with telomere dysfunction, telomerase reactivation in the intestinal epithelium or pharmacological inhibition of ATM, YAP1, or caspase-1 as well as antibiotic treatment, dramatically reduces IL-18 and intestinal inflammation. Thus, telomere dysfunction-induced activation of the ATM-YAP1-pro-IL-18 pathway in epithelium is a key instigator of tissue inflammation.


Assuntos
Proteínas Adaptadoras de Transdução de Sinal/metabolismo , Proteínas de Ciclo Celular/metabolismo , Inflamação/patologia , Telômero/patologia , Proteínas Adaptadoras de Transdução de Sinal/antagonistas & inibidores , Proteínas Adaptadoras de Transdução de Sinal/genética , Animais , Antibacterianos/uso terapêutico , Proteínas Mutadas de Ataxia Telangiectasia/antagonistas & inibidores , Proteínas Mutadas de Ataxia Telangiectasia/metabolismo , Caspase 1/metabolismo , Proteínas de Ciclo Celular/antagonistas & inibidores , Proteínas de Ciclo Celular/genética , Criança , Colo/metabolismo , Colo/microbiologia , Colo/patologia , Gastroenteropatias/patologia , Microbioma Gastrointestinal/efeitos dos fármacos , Microbioma Gastrointestinal/fisiologia , Humanos , Inflamação/tratamento farmacológico , Inflamação/metabolismo , Inflamação/microbiologia , Interleucina-18/genética , Interleucina-18/metabolismo , Mucosa Intestinal/metabolismo , Mucosa Intestinal/patologia , Camundongos , Camundongos Mutantes , Fosforilação , Precursores de Proteínas/genética , Precursores de Proteínas/metabolismo , Transdução de Sinais , Telomerase/genética , Telomerase/metabolismo
4.
Proc Natl Acad Sci U S A ; 117(36): 22068-22079, 2020 09 08.
Artigo em Inglês | MEDLINE | ID: mdl-32839320

RESUMO

RNA-protein interactions underlie a wide range of cellular processes. Improved methods are needed to systematically map RNA-protein interactions in living cells in an unbiased manner. We used two approaches to target the engineered peroxidase APEX2 to specific cellular RNAs for RNA-centered proximity biotinylation of protein interaction partners. Both an MS2-MCP system and an engineered CRISPR-Cas13 system were used to deliver APEX2 to the human telomerase RNA hTR with high specificity. One-minute proximity biotinylation captured candidate binding partners for hTR, including more than a dozen proteins not previously linked to hTR. We validated the interaction between hTR and the N 6-methyladenosine (m6A) demethylase ALKBH5 and showed that ALKBH5 is able to erase the m6A modification on endogenous hTR. ALKBH5 also modulates telomerase complex assembly and activity. MS2- and Cas13-targeted APEX2 may facilitate the discovery of novel RNA-protein interactions in living cells.


Assuntos
DNA Liase (Sítios Apurínicos ou Apirimidínicos)/metabolismo , Endonucleases/metabolismo , Enzimas Multifuncionais/metabolismo , Mapeamento de Interação de Proteínas/métodos , RNA/metabolismo , Telomerase/metabolismo , Homólogo AlkB 5 da RNA Desmetilase/genética , Homólogo AlkB 5 da RNA Desmetilase/metabolismo , Biotinilação , Sistemas CRISPR-Cas , Metilação de DNA , DNA Liase (Sítios Apurínicos ou Apirimidínicos)/genética , Endonucleases/genética , Células HEK293 , Humanos , Espectrometria de Massas , Enzimas Multifuncionais/genética , Ligação Proteica , RNA/genética , Telomerase/genética
5.
Nutr Metab Cardiovasc Dis ; 30(10): 1795-1799, 2020 09 24.
Artigo em Inglês | MEDLINE | ID: mdl-32723580

RESUMO

Type 2 Diabetes mellitus is associated with aging and shortened telomere length. Telomerase replaces lost telomeric repeats at the ends of chromosomes and is necessary for the replicative immortality of cells. Aspirin and the n3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are commonly used therapies in people with type 2 diabetes for reducing cardiovascular disease events, though their relation to telomerase activity is not well studied. We explored the effects of aspirin, EPA + DHA, and the combined effects of aspirin and EPA + DHA treatment on telomerase activity in 30 adults with diabetes mellitus. EPA and DHA ingestion alone increased telomerase activity then a decrease occurred with the addition of aspirin consumption. Crude (F-stat = 2.09, p = 0.13) and adjusted (F-stat = 2.20, p = 0.14) analyses of this decrease showed signs of a trend. These results suggest that aspirin has an adverse effect on aging in diabetics who have relatively high EPA and DHA ingestion.


Assuntos
Aspirina/administração & dosagem , Diabetes Mellitus Tipo 2/tratamento farmacológico , Ácidos Docosa-Hexaenoicos/administração & dosagem , Ácido Eicosapentaenoico/administração & dosagem , Telomerase/metabolismo , Homeostase do Telômero/efeitos dos fármacos , Adulto , Idoso , Idoso de 80 Anos ou mais , Aspirina/efeitos adversos , Diabetes Mellitus Tipo 2/diagnóstico , Diabetes Mellitus Tipo 2/enzimologia , Ácidos Docosa-Hexaenoicos/efeitos adversos , Ácido Eicosapentaenoico/efeitos adversos , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , New York , Resultado do Tratamento
6.
Life Sci ; 257: 118115, 2020 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-32698073

RESUMO

Telomerase plays a significant role to maintain and regulate the telomere length, cellular immortality and senescence by the addition of guanine-rich repetitive sequences. Chronic inflammation or oxidative stress-induced infection downregulates TERT gene modifying telomerase activity thus contributing to the early steps of gastric carcinogenesis process. Furthermore, telomere-telomerase system performs fundamental role in the pathogenesis and progression of diabetes mellitus as well as in its vascular intricacy. The cessation of cell proliferation in cultured cells by inhibiting the telomerase activity of transformed cells renders the rationale for culling of telomerase as a target therapy for the treatment of metabolic disorders and various types of cancers. In this article, we have briefly described the role of immune system and malignant cells in the expression of telomerase with critical analysis on the gaps and potential for future studies. The key findings regarding the secrets of the telomerase summarized in this article will help in future treatment modalities for the prevention of various types of cancers and metabolic disorders notably diabetes mellitus.


Assuntos
Telomerase/metabolismo , Envelhecimento/metabolismo , Animais , Diabetes Mellitus/enzimologia , Humanos , Neoplasias/enzimologia , Telomerase/antagonistas & inibidores , Telomerase/fisiologia , Encurtamento do Telômero
7.
J Cancer Res Clin Oncol ; 146(11): 2753-2775, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32681293

RESUMO

INTRODUCTION: hTERT (human telomerase reverse transcriptase) is a catalytic subunit of the enzyme telomerase and has a role in cell proliferation, cellular senescence, and human aging. MATERIALS AND METHODS: The purpose of this study was to evaluate the expression and significance of hTERT protein expression as a prognostic marker in different histological subtypes of testicular germ cell tumors (TGCTs), including 46 embryonal carcinomas, 46 yolk sac tumors, 38 teratomas, 84 seminomas as well as two main subtypes of seminomas and non-seminomas using tissue microarray (TMA) technique. RESULTS: The results showed that there is a statistically significance difference between the expression of hTERT and various histological subtypes of TGCTs (P < 0.001). In embryonal carcinoma, low level expression of hTERT protein was significantly associated with advanced pT stage (P = 0.023) as well as tunica vaginalis invasion (P = 0.043). Moreover, low level expression of hTERT protein was found to be a significant predictor of worse DSS (log rank: P = 0.011) and PFS (log rank: P = 0.011) in the univariate analysis. Additionally, significant differences were observed (P =0.021, P =0.018) with 5-year survival rates for DSS and PFS of 66% and 70% for moderate as compared to 97% and 97% for high hTERT protein expression, respectively. CONCLUSION: We showed that hTERT protein expression was associated with more aggressive tumor behavior in embryonal carcinoma patients. Also, hTERT may be a novel worse prognostic indicator of DSS or PFS, if the patients are followed up for more time periods.


Assuntos
Biomarcadores Tumorais/metabolismo , Carcinoma Embrionário/enzimologia , Telomerase/metabolismo , Neoplasias Testiculares/enzimologia , Adolescente , Adulto , Biomarcadores Tumorais/análise , Carcinoma Embrionário/mortalidade , Carcinoma Embrionário/patologia , Progressão da Doença , Humanos , Masculino , Pessoa de Meia-Idade , Intervalo Livre de Progressão , Telomerase/análise , Neoplasias Testiculares/mortalidade , Neoplasias Testiculares/patologia , Adulto Jovem
8.
Arterioscler Thromb Vasc Biol ; 40(9): 2244-2264, 2020 09.
Artigo em Inglês | MEDLINE | ID: mdl-32640900

RESUMO

OBJECTIVE: Nanog is expressed in adult endothelial cells (ECs) at a low-level, however, its functional significance is not known. The goal of our study was to elucidate the role of Nanog in adult ECs using a genetically engineered mouse model system. Approach and Results: Biochemical analyses showed that Nanog is expressed in both adult human and mouse tissues. Primary ECs isolated from adult mice showed detectable levels of Nanog, Tert (telomerase reverse transcriptase), and eNos (endothelial nitric oxide synthase). Wnt3a (Wnt family member 3A) increased the expression of Nanog and hTERT (human telomerase reverse transcriptase) in ECs and increased telomerase activity in these cells. In a chromatin immunoprecipitation experiment, Nanog directly bound to the hTERT and eNOS promoter/enhancer DNA elements, thereby regulating their transcription. Administration of low-dose tamoxifen to ROSAmT/mG::Nanogfl/+::Cdh5CreERT2 mice induced deletion of a single Nanog allele, simultaneously labeling ECs with green fluorescent protein and resulting in decreased Tert and eNos levels. Histological and morphometric analyses of heart tissue sections prepared from these mice revealed cell death, microvascular rarefaction, and increased fibrosis in cardiac vessels. Accordingly, EC-specific Nanog-haploinsufficiency resulted in impaired EC homeostasis and angiogenesis. Conversely, re-expression of cDNA encoding the hTERT in Nanog-depleted ECs, in part, restored the effect of loss of Nanog. CONCLUSIONS: We showed that low-level Nanog expression is required for normal EC homeostasis and angiogenesis in adulthood.


Assuntos
Proliferação de Células , Senescência Celular , Vasos Coronários/metabolismo , Células Endoteliais/metabolismo , Endotélio Vascular/metabolismo , Proteína Homeobox Nanog/metabolismo , Animais , Apoptose , Proliferação de Células/efeitos dos fármacos , Células Cultivadas , Senescência Celular/efeitos dos fármacos , Vasos Coronários/efeitos dos fármacos , Vasos Coronários/patologia , Células Endoteliais/efeitos dos fármacos , Células Endoteliais/patologia , Endotélio Vascular/efeitos dos fármacos , Endotélio Vascular/patologia , Feminino , Fibrose , Células Endoteliais da Veia Umbilical Humana/metabolismo , Humanos , Masculino , Camundongos Endogâmicos C57BL , Camundongos Knockout , Proteína Homeobox Nanog/deficiência , Proteína Homeobox Nanog/genética , Neovascularização Fisiológica , Óxido Nítrico Sintase Tipo III/genética , Óxido Nítrico Sintase Tipo III/metabolismo , Telomerase/genética , Telomerase/metabolismo , Ativação Transcricional , Via de Sinalização Wnt , Proteína Wnt3A/farmacologia
9.
Biomed Khim ; 66(3): 265-273, 2020 May.
Artigo em Russo | MEDLINE | ID: mdl-32588833

RESUMO

In proliferating normal and tumor cells, the telomere length (TL) is maintained by high telomerase activity (TA). In the absence of TA the TL maintenance involves a mechanism of alternative lengthening of telomeres (ALT). The aim of this study was to investigate the level of TA, the mTert expression and TL in cultured normal and transformed by γ- and γ,n-irradiation mesenchymal stem cells (MSCs) from mouse bone marrow, in sarcomas that developed after the transplantation of these cells into syngeneic mice, and in fibrosarcoma cell lines obtained from these tumors to find out the role of AT or ALT in maintaining TL in these cells. During prolonged cultivation of normal and transformed under the influence of γ- (1 Gy and 6 Gy) and γ,n-irradiation (0.05 Gy, 0.5 Gy, and 2 Gy) MSCs from mouse bone marrow, a decrease in TA was detected in irradiated cells. Even deeper decrease in TA was found in sarcomas developed after administration of transformed MSCs to syngeneic mice and in fibrosarcoma cell lines isolated from these tumors in which TA was either absent or was found to be at a very low level. TL in three of the four lines obtained was halved compared to the initial MSCs. With absent or low TA and reduced TL, the cells of all the obtained fibrosarcoma lines successfully proliferated without signs of a change in survival. The mechanism of telomere maintainance in fibrosarcoma cell lines in the absence of TA needs further investigation and it can be assumed that it is associated with the use of the ALT. The detected decrease or absence of TA in transformed under the action of irradiation MSCs with the preservation or even an increase in the telomerase gene expression may be associated with the formation of inactive splicing variants, and requires further study. The obtained lines of transformed MSCs and fibrosarcomas with TA and without the activity of this enzyme can be a useful model for studying the efficacy of TA and ALT inhibitors in vitro and in vivo.


Assuntos
Raios gama , Células-Tronco Mesenquimais , Telomerase , Telômero , Animais , Linhagem Celular , Fibrossarcoma/patologia , Camundongos , Telomerase/genética , Telomerase/metabolismo , Telômero/genética
10.
Cell Stem Cell ; 26(6): 804-805, 2020 06 04.
Artigo em Inglês | MEDLINE | ID: mdl-32502401

RESUMO

Most rare inherited telomere biology disorders and some common aging-related diseases are associated with shortened telomeres. In this issue of Cell Stem Cell, insights into one of the rarest genetic causes of these disorders led to the discovery (Nagpal et al., 2020) of small molecules that lengthen telomeres.


Assuntos
Telomerase , Telômero , Humanos , Células-Tronco/metabolismo , Telomerase/metabolismo , Telômero/genética , Telômero/metabolismo , Encurtamento do Telômero
11.
Clin Interv Aging ; 15: 827-839, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32581523

RESUMO

Different factors influence the development and control of ageing. It is well known that progressive telomere shorting is one of the molecular mechanisms underlying ageing. The shelterin complex consists of six telomere-specific proteins which are involved in the protection of chromosome ends. More particularly, this vital complex protects the telomeres from degradation, prevents from activation of unwanted repair systems, regulates the activity of telomerase, and has a crucial role in cellular senescent and ageing-related pathologies. This review explores the organization and function of telomeric DNA along with the mechanism of telomeres during ageing, followed by a discussion of the critical role of shelterin components and their changes during ageing.


Assuntos
Envelhecimento/metabolismo , Estresse Oxidativo , Telomerase/metabolismo , Proteínas de Ligação a Telômeros/metabolismo , Telômero/metabolismo , Envelhecimento/genética , Replicação do DNA , Humanos , Proteínas de Ligação a Telômeros/genética
12.
Cancer Sci ; 111(9): 3089-3099, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32579791

RESUMO

The telomere is the specialized nucleoprotein complex at the end of the chromosome. Its highly conserved 5'-TTAGGG-3' repeats and shelterin protein complexes form a protective loop structure to maintain the integrity and stability of linear chromosomes. Although human somatic cells gradually shorten telomeres to undergo senescence or crisis, cancer cells activate telomerase, or the recombination-based mechanism to maintain telomeres and exhibit immortality. As the most frequent non-coding mutations in cancer, gain-of-function mutations in the promoter region of the telomerase catalytic subunit, TERT, trigger telomerase activation. Promoter methylation and copy number gain are also associated with the enhanced TERT expression. Although telomerase inhibitors were pioneered from telomere-directed therapeutics, their efficacies are limited to cancer with short telomeres and some hematological malignancies. Other therapeutic approaches include a nucleoside analog incorporated to telomeres and TERT promoter-driven oncolytic adenoviruses. Tankyrase poly(ADP-ribose) polymerase, a positive regulator of telomerase, has been rediscovered as a target for Wnt-driven cancer. Meanwhile, telomeric nucleic acids form a higher-order structure called a G-quadruplex (G4). G4s are formed genome-wide and their dynamics affect various events, including replication, transcription, and translation. G4-stabilizing compounds (G4 ligands) exert anticancer effects and are in clinical investigations. Collectively, telomere biology has provided clues for deeper understanding of cancer, which expands opportunities to discover innovative anticancer drugs.


Assuntos
Antineoplásicos/farmacologia , Descoberta de Drogas , Telômero/efeitos dos fármacos , Animais , Antineoplásicos/uso terapêutico , Transformação Celular Neoplásica/genética , Quadruplex G/efeitos dos fármacos , Terapia Genética , Humanos , Ligantes , Neoplasias/tratamento farmacológico , Neoplasias/genética , Neoplasias/patologia , Terapia Viral Oncolítica , Regiões Promotoras Genéticas , RNA não Traduzido/genética , Telomerase/genética , Telomerase/metabolismo , Telômero/genética , Encurtamento do Telômero/efeitos dos fármacos
13.
Toxicol Appl Pharmacol ; 401: 115079, 2020 08 15.
Artigo em Inglês | MEDLINE | ID: mdl-32497534

RESUMO

Thioredoxin 1 (Trx1) and telomerase play key roles in the development and progression process of most tumors, and they both are promising drug therapy targets. We have, for the first time, discovered that Trx1 and telomerase had a dual-target synergistic effect. Based on that results, we designed a series of 6-dithio-2'-deoxyguanosine analogs (named as YLS00X) and verified whether they can inhibit Trx1 and telomerase simultaneously. TrxR1/Trx1 system activity and telomerase expression were significantly inhibited by 6-dithio-2'-deoxyguanosine analogs, especially YLS004. YLS004 can also cause ROS accumulation, and induce tumor cell apoptosis. The vitro antitumor activity of 6-dithio-2'-deoxyguanosine analogs using MTT assay on 11 different human cancer cells and found that human colon cancer cells(HCT116) and melanoma cells (A375) were the most sensitive cells to 6-dithio-2'-deoxyguanosine analogs treatment and vivo xenografts models also confirmed that. The serum biochemical parameters and multiple organs HE staining results of subacute experiments indicated that YLS004 might be mildly toxic to immune organs, including the thymus, spleen, and hematopoietic system. Besides, YLS004 was rapidly metabolized in the rats' blood. Our study revealed that YLS004, a Trx1 and telomerase inhibitor, has strong anti-tumor effects to colon cancer and melanoma cells and is a promising new candidate drug.


Assuntos
Desoxiguanosina/análogos & derivados , Desoxiguanosina/administração & dosagem , Sistemas de Liberação de Medicamentos/métodos , Espécies Reativas de Oxigênio/agonistas , Telomerase/antagonistas & inibidores , Tiorredoxinas/antagonistas & inibidores , Células A549 , Animais , Antineoplásicos/administração & dosagem , Antineoplásicos/química , Apoptose/efeitos dos fármacos , Apoptose/fisiologia , Linhagem Celular Tumoral , Sobrevivência Celular/efeitos dos fármacos , Sobrevivência Celular/fisiologia , Relação Dose-Resposta a Droga , Células HCT116 , Células HT29 , Células Hep G2 , Humanos , Células K562 , Masculino , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Nus , Ratos , Espécies Reativas de Oxigênio/metabolismo , Telomerase/metabolismo , Tiorredoxinas/metabolismo
14.
Nucleic Acids Res ; 48(13): 7239-7251, 2020 07 27.
Artigo em Inglês | MEDLINE | ID: mdl-32542379

RESUMO

Telomeres cap the ends of eukaryotic chromosomes and distinguish them from broken DNA ends to suppress DNA damage response, cell cycle arrest and genomic instability. Telomeres are elongated by telomerase to compensate for incomplete replication and nuclease degradation and to extend the proliferation potential of germ and stem cells and most cancers. However, telomeres in somatic cells gradually shorten with age, ultimately leading to cellular senescence. Hoyeraal-Hreidarsson syndrome (HHS) is characterized by accelerated telomere shortening and diverse symptoms including bone marrow failure, immunodeficiency, and neurodevelopmental defects. HHS is caused by germline mutations in telomerase subunits, factors essential for its biogenesis and recruitment to telomeres, and in the helicase RTEL1. While diverse phenotypes were associated with RTEL1 deficiency, the telomeric role of RTEL1 affected in HHS is yet unknown. Inducible ectopic expression of wild-type RTEL1 in patient fibroblasts rescued the cells, enabled telomerase-dependent telomere elongation and suppressed the abnormal cellular phenotypes, while silencing its expression resulted in gradual telomere shortening. Our observations reveal an essential role of the RTEL1 C-terminus in facilitating telomerase action at the telomeric 3' overhang. Thus, the common etiology for HHS is the compromised telomerase action, resulting in telomere shortening and reduced lifespan of telomerase positive cells.


Assuntos
DNA Helicases/metabolismo , Disceratose Congênita/genética , Retardo do Crescimento Fetal/genética , Deficiência Intelectual/genética , Microcefalia/genética , Homeostase do Telômero , Células Cultivadas , DNA Helicases/química , DNA Helicases/genética , Fibroblastos/metabolismo , Humanos , Domínios Proteicos , Telomerase/genética , Telomerase/metabolismo , Encurtamento do Telômero
15.
Trends Pharmacol Sci ; 41(8): 506-508, 2020 08.
Artigo em Inglês | MEDLINE | ID: mdl-32482456

RESUMO

Genetic defects in telomere maintenance result in stem cell exhaustion and a spectrum of telomere biology diseases. Systemic treatments beyond organ transplantation are lacking for these diseases. Nagpal and colleagues identified small molecules that restore telomere maintenance in patient-derived stem cells, offering a promising therapy for telomere biology diseases.


Assuntos
Disceratose Congênita , Telomerase , Humanos , RNA , Células-Tronco/metabolismo , Telomerase/genética , Telomerase/metabolismo , Telômero/metabolismo
16.
Proc Natl Acad Sci U S A ; 117(26): 15066-15074, 2020 06 30.
Artigo em Inglês | MEDLINE | ID: mdl-32554492

RESUMO

Cancer incidence increases exponentially with age when human telomeres are shorter. Similarly, telomerase reverse transcriptase (tert) mutant zebrafish have premature short telomeres and anticipate cancer incidence to younger ages. However, because short telomeres constitute a road block to cell proliferation, telomere shortening is currently viewed as a tumor suppressor mechanism and should protect from cancer. This conundrum is not fully understood. In our current study, we report that telomere shortening promotes cancer in a noncell autonomous manner. Using zebrafish chimeras, we show increased incidence of invasive melanoma when wild-type (WT) tumors are generated in tert mutant zebrafish. Tissues adjacent to melanoma lesions (skin) and distant organs (intestine) in tert mutants exhibited higher levels of senescence and inflammation. In addition, we transferred second generation (G2) tert blastula cells into WT to produce embryo chimeras. Cells with very short telomeres induced increased tumor necrosis factor1-α (TNF1-α) expression and senescence in larval tissues in a noncell autonomous manner, creating an inflammatory environment. Considering that inflammation is protumorigenic, we transplanted melanoma-derived cells into G2 tert zebrafish embryos and observed that tissue environment with short telomeres leads to increased tumor development. To test if inflammation was necessary for this effect, we treated melanoma transplants with nonsteroid anti-inflammatory drugs and show that higher melanoma dissemination can be averted. Thus, apart from the cell autonomous role of short telomeres in contributing to genome instability, we propose that telomere shortening with age causes systemic chronic inflammation leading to increased tumor incidence.


Assuntos
Melanoma/metabolismo , Telômero/metabolismo , Peixe-Zebra/metabolismo , Animais , Modelos Animais de Doenças , Humanos , Melanoma/genética , Melanoma/imunologia , Telomerase/genética , Telomerase/metabolismo , Telômero/genética , Encurtamento do Telômero , Fator de Necrose Tumoral alfa/genética , Fator de Necrose Tumoral alfa/imunologia , Peixe-Zebra/genética , Peixe-Zebra/imunologia , Proteínas de Peixe-Zebra/genética , Proteínas de Peixe-Zebra/metabolismo
17.
Mol Cell ; 79(1): 115-126.e6, 2020 07 02.
Artigo em Inglês | MEDLINE | ID: mdl-32497497

RESUMO

Extension of telomeres is a critical step in the immortalization of cancer cells. This complex reaction requires proper spatiotemporal coordination of telomerase and telomeres and remains poorly understood at the cellular level. To understand how cancer cells execute this process, we combine CRISPR genome editing and MS2 RNA tagging to image single molecules of telomerase RNA (hTR). Real-time dynamics and photoactivation experiments of hTR in Cajal bodies (CBs) reveal that hTERT controls the exit of hTR from CBs. Single-molecule tracking of hTR at telomeres shows that TPP1-mediated recruitment results in short telomere-telomerase scanning interactions, and then base pairing between hTR and telomere ssDNA promotes long interactions required for stable telomerase retention. Interestingly, POT1 OB-fold mutations that result in abnormally long telomeres in cancers act by enhancing this retention step. In summary, single-molecule imaging unveils the life cycle of telomerase RNA and provides a framework to reveal how cancer-associated mutations mechanistically drive defects in telomere homeostasis.


Assuntos
Corpos Enovelados/metabolismo , DNA de Cadeia Simples/metabolismo , RNA/metabolismo , Imagem Individual de Molécula/métodos , Telomerase/metabolismo , Homeostase do Telômero , Telômero/metabolismo , Repetições Palindrômicas Curtas Agrupadas e Regularmente Espaçadas , DNA de Cadeia Simples/genética , Edição de Genes , Células HeLa , Humanos , Mutação , RNA/genética , Telomerase/genética , Telômero/genética , Proteínas de Ligação a Telômeros/genética , Proteínas de Ligação a Telômeros/metabolismo
18.
Nat Commun ; 11(1): 2173, 2020 05 01.
Artigo em Inglês | MEDLINE | ID: mdl-32358529

RESUMO

RNase P and MRP are highly conserved, multi-protein/RNA complexes with essential roles in processing ribosomal and tRNAs. Three proteins found in both complexes, Pop1, Pop6, and Pop7 are also telomerase-associated. Here, we determine how temperature sensitive POP1 and POP6 alleles affect yeast telomerase. At permissive temperatures, mutant Pop1/6 have little or no effect on cell growth, global protein levels, the abundance of Est1 and Est2 (telomerase proteins), and the processing of TLC1 (telomerase RNA). However, in pop mutants, TLC1 is more abundant, telomeres are short, and TLC1 accumulates in the cytoplasm. Although Est1/2 binding to TLC1 occurs at normal levels, Est1 (and hence Est3) binding is highly unstable. We propose that Pop-mediated stabilization of Est1 binding to TLC1 is a pre-requisite for formation and nuclear localization of the telomerase holoenzyme. Furthermore, Pop proteins affect TLC1 and the RNA subunits of RNase P/MRP in very different ways.


Assuntos
Ribonuclease P/metabolismo , Ribonucleoproteínas/metabolismo , Proteínas de Saccharomyces cerevisiae/metabolismo , Saccharomyces cerevisiae/metabolismo , Telomerase/metabolismo , Telômero/metabolismo , Núcleo Celular/genética , Núcleo Celular/metabolismo , Proteínas de Ligação a DNA/genética , Proteínas de Ligação a DNA/metabolismo , Metilação , Ligação Proteica , RNA/metabolismo , Processamento de Terminações 3' de RNA/genética , Ribonuclease P/genética , Ribonucleoproteínas/genética , Proteínas de Saccharomyces cerevisiae/genética , Telomerase/genética , Telômero/química
19.
PLoS One ; 15(4): e0231418, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32267900

RESUMO

The telomerase reverse transcriptase (TERT) gene is responsible for telomere maintenance in germline and stem cells, and is re-expressed in 90% of human cancers. CpG methylation in the TERT promoter (TERTp) was correlated with TERT mRNA expression. Furthermore, two hotspot mutations in TERTp, dubbed C228T and C250T, have been revealed to facilitate binding of transcription factor ETS/TCF and subsequent TERT expression. This study aimed to elucidate the combined contribution of epigenetic (promoter methylation and chromatin accessibility) and genetic (promoter mutations) mechanisms in regulating TERT gene expression in healthy skin samples and in melanoma cell lines (n = 61). We unexpectedly observed that the methylation of TERTp was as high in a subset of healthy skin cells, mainly keratinocytes, as in cutaneous melanoma cell lines. In spite of the high promoter methylation fraction in wild-type (WT) samples, TERT mRNA was only expressed in the melanoma cell lines with either high methylation or intermediate methylation in combination with TERT mutations. TERTp methylation was positively correlated with chromatin accessibility and TERT mRNA expression in 8 melanoma cell lines. Cooperation between epigenetic and genetic mechanisms were best observed in heterozygous mutant cell lines as chromosome accessibility preferentially concerned the mutant allele. Combined, these results suggest a complex model in which TERT expression requires either a widely open chromatin state in TERTp-WT samples due to high methylation throughout the promoter or a combination of moderate methylation fraction/chromatin accessibility in the presence of the C228T or C250T mutations.


Assuntos
Cromatina/metabolismo , Metilação de DNA , Telomerase/metabolismo , Alelos , Linhagem Celular , Cromatina/química , Montagem e Desmontagem da Cromatina , Ilhas de CpG , Humanos , Queratinócitos/citologia , Queratinócitos/metabolismo , Melanoma/genética , Melanoma/patologia , Mutação , Regiões Promotoras Genéticas , Ligação Proteica , RNA Mensageiro/metabolismo , Neoplasias Cutâneas/genética , Neoplasias Cutâneas/patologia , Telomerase/genética , Fatores de Transcrição/química , Fatores de Transcrição/metabolismo
20.
Nat Rev Mol Cell Biol ; 21(7): 384-397, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-32242127

RESUMO

Telomerase is a ribonucleoprotein complex, the catalytic core of which includes the telomerase reverse transcriptase (TERT) and the non-coding human telomerase RNA (hTR), which serves as a template for the addition of telomeric repeats to chromosome ends. Telomerase expression is restricted in humans to certain cell types, and telomerase levels are tightly controlled in normal conditions. Increased levels of telomerase are found in the vast majority of human cancers, and we have recently begun to understand the mechanisms by which cancer cells increase telomerase activity. Conversely, germline mutations in telomerase-relevant genes that decrease telomerase function cause a range of genetic disorders, including dyskeratosis congenita, idiopathic pulmonary fibrosis and bone marrow failure. In this Review, we discuss the transcriptional regulation of human TERT, hTR processing, assembly of the telomerase complex, the cellular localization of telomerase and its recruitment to telomeres, and the regulation of telomerase activity. We also discuss the disease relevance of each of these steps of telomerase biogenesis.


Assuntos
Regulação da Expressão Gênica , Homeostase , Mutação , Neoplasias/genética , Neoplasias/patologia , Telomerase/metabolismo , Telômero/fisiologia , Humanos , Neoplasias/metabolismo
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