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1.
Adv Exp Med Biol ; 1192: 521-544, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31705512

RESUMO

Major psychiatric disorders are linked to early mortality and patients afflicted with these ailments demonstrate an increased risk of developing physical diseases that are characteristically seen in the elderly. Psychiatric conditions like major depressive disorder, bipolar disorder, and schizophrenia may be associated with accelerated cellular aging, indicated by shortened leukocyte telomere length (LTL), which could underlie this connection. Telomere shortening occurs with repeated cell division and is reflective of a cell's mitotic history. It is also influenced by cumulative exposure to inflammation and oxidative stress as well as the availability of telomerase, the telomere-lengthening enzyme. Precariously short telomeres can cause cells to undergo senescence, apoptosis, or genomic instability; shorter LTL correlates with compromised general health and foretells mortality. Important data specify that LTL may be reduced in principal psychiatric illnesses, possibly in proportion to exposure to the ailment. Telomerase, as measured in peripheral blood monocytes, has been less well characterized in psychiatric illnesses, but a role in mood disorder has been suggested by preclinical and clinical studies. In this manuscript, the most recent studies on LTL and telomerase activity in mood disorders are comprehensively reviewed, potential mediators are discussed, and future directions are suggested. An enhanced comprehension of cellular aging in psychiatric illnesses could lead to their re-conceptualizing as systemic ailments with manifestations both inside and outside the brain. At the same time, this paradigm shift could identify new treatment targets, helpful in bringing about lasting cures to innumerable sufferers across the globe.


Assuntos
Senescência Celular/genética , Leucócitos/metabolismo , Transtornos Mentais/genética , Telomerase , Telômero/metabolismo , Idoso , Humanos , Transtornos Mentais/diagnóstico , Homeostase do Telômero , Encurtamento do Telômero
2.
Georgian Med News ; (291): 58-63, 2019 Jun.
Artigo em Russo | MEDLINE | ID: mdl-31418732

RESUMO

Aim - to determine the influence of different levels of lipid metabolism on the relative blood leukocytes telomeres length (RLTL), relative buccal epithelium cells telomeres length (RBTL) in hypertensive (H) individuals with type 2 diabetes mellitus (DM2T) and without DM2T. In 60 patients with H stage II (group 1), and 96 patients with H and DM2T (group 2) lipid metabolism indexes (total cholesterol (TC), triglycerides (TG), low density lipoprotein cholesterol (LDL-C), high density lipoprotein cholesterol (HDL-C)), anthropometric parameters were measured. Relative telomeres length (RTL) was determined by a real time quantitative PCR. The most significant shortening of RLTL and RBTL were found in group 2. In both groups, the achievement of target blood lipid levels was accompanied by multidirectional changes in RTL. Analysis of variance revealed a significant effect of TC (p=0.036) on the RBTL, LDL -C (p=0.036) on the RBTL in group 1, and significant influence of TG (p = 0.049) on RBTL, TC (p=0.019) and HDL-C (p=0.032) on RLTL in group 2. Achieving target levels of lipid metabolism did not demonstrate the expected significant effect on the elongation of the relative length of telomeres, both with isolated hypertension and with a combined course of hypertension and DM2T.


Assuntos
Diabetes Mellitus Tipo 2/complicações , Diabetes Mellitus Tipo 2/metabolismo , Hipertensão/complicações , Hipertensão/metabolismo , Metabolismo dos Lipídeos , Telômero/metabolismo , HDL-Colesterol , LDL-Colesterol , Diabetes Mellitus Tipo 2/genética , Humanos , Hipertensão/genética , Telômero/genética , Encurtamento do Telômero , Triglicerídeos
3.
High Blood Press Cardiovasc Prev ; 26(4): 321-329, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31325087

RESUMO

Cardiovascular disease (CVD) remains the leading cause of morbility and mortality worldwide. The identification of common cardiovascular risk factors has led to the development of effective treatments that enabled a significant reduction of the global cardiovascular disease burden. However, a significant proportion of cardiovascular risk remains unexplained by these risk factors leaving many individuals at risk of cardiovascular events despite good control of the risk factors. Recent randomized clinical trials and Mendelian randomization studies have suggested that inflammation explains a significant proportion of the residual cardiovascular risk in subjects with good control of risk factors. An accelerated process of vascular ageing is increasingly recognized as a potential mechanism by which inflammation might increase the risk of CVD. In turn, cellular ageing represents an important source of inflammation within the vascular wall, potentially creating a vicious cycle that might promote progression of atherosclerosis, independently from the individual cardiovascular risk factor burden. In this review, we summarise current evidence suggesting a role for biological ageing in CVD and how inflammation might act as a key mediator of this association.


Assuntos
Envelhecimento/metabolismo , Doenças Cardiovasculares/metabolismo , Mediadores da Inflamação/metabolismo , Inflamação/metabolismo , Telômero/metabolismo , Fatores Etários , Envelhecimento/genética , Envelhecimento/patologia , Animais , Doenças Cardiovasculares/genética , Doenças Cardiovasculares/patologia , Doenças Cardiovasculares/fisiopatologia , Senescência Celular , Humanos , Inflamação/genética , Inflamação/patologia , Inflamação/fisiopatologia , Medição de Risco , Fatores de Risco , Transdução de Sinais , Telômero/genética , Telômero/patologia , Homeostase do Telômero , Encurtamento do Telômero , Fatores de Tempo
4.
Nat Rev Gastroenterol Hepatol ; 16(9): 544-558, 2019 09.
Artigo em Inglês | MEDLINE | ID: mdl-31253940

RESUMO

Telomerase is a key enzyme for cell survival that prevents telomere shortening and the subsequent cellular senescence that is observed after many rounds of cell division. In contrast, inactivation of telomerase is observed in most cells of the adult liver. Absence of telomerase activity and shortening of telomeres has been implicated in hepatocyte senescence and the development of cirrhosis, a chronic liver disease that can lead to hepatocellular carcinoma (HCC) development. During hepatocarcinogenesis, telomerase reactivation is required to enable the uncontrolled cell proliferation that leads to malignant transformation and HCC development. Part of the telomerase complex, telomerase reverse transcriptase, is encoded by TERT, and several mechanisms of telomerase reactivation have been described in HCC that include somatic TERT promoter mutations, TERT amplification, TERT translocation and viral insertion into the TERT gene. An understanding of the role of telomeres and telomerase in HCC development is important to develop future targeted therapies and improve survival of this disease. In this Review, the roles of telomeres and telomerase in liver carcinogenesis are discussed, in addition to their potential translation to clinical practice as biomarkers and therapeutic targets.


Assuntos
Carcinoma Hepatocelular/metabolismo , Cirrose Hepática/metabolismo , Neoplasias Hepáticas/metabolismo , Telomerase/metabolismo , Telômero/metabolismo , Animais , Biomarcadores Tumorais/genética , Biomarcadores Tumorais/metabolismo , Carcinoma Hepatocelular/genética , Divisão Celular/fisiologia , Sobrevivência Celular/fisiologia , Transformação Celular Neoplásica/genética , Transformação Celular Neoplásica/metabolismo , Modelos Animais de Doenças , Humanos , Fígado/metabolismo , Cirrose Hepática/genética , Neoplasias Hepáticas/genética , Camundongos , Mutação , Telomerase/genética , Telômero/genética
5.
Genes Dev ; 33(13-14): 814-827, 2019 07 01.
Artigo em Inglês | MEDLINE | ID: mdl-31171703

RESUMO

Alternative lengthening of telomeres (ALT) is a telomerase-independent telomere maintenance mechanism that occurs in a subset of cancers. One of the hallmarks of ALT cancer is the excessively clustered telomeres in promyelocytic leukemia (PML) bodies, represented as large bright telomere foci. Here, we present a model system that generates telomere clustering in nuclear polySUMO (small ubiquitin-like modification)/polySIM (SUMO-interacting motif) condensates, analogous to PML bodies, and thus artificially engineered ALT-associated PML body (APB)-like condensates in vivo. We observed that the ALT-like phenotypes (i.e., a small fraction of heterogeneous telomere lengths and formation of C circles) are rapidly induced by introducing the APB-like condensates together with BLM through its helicase domain, accompanied by ssDNA generation and RPA accumulation at telomeres. Moreover, these events lead to mitotic DNA synthesis (MiDAS) at telomeres mediated by RAD52 through its highly conserved N-terminal domain. We propose that the clustering of large amounts of telomeres in human cancers promotes ALT that is mediated by MiDAS, analogous to Saccharomyces cerevisiae type II ALT survivors.


Assuntos
Núcleo Celular/metabolismo , DNA/biossíntese , Leucemia Promielocítica Aguda/fisiopatologia , Mitose , Proteína Rad52 de Recombinação e Reparo de DNA/metabolismo , RecQ Helicases/metabolismo , Homeostase do Telômero/genética , Motivos de Aminoácidos , Linhagem Celular Tumoral , Expressão Gênica , Humanos , Leucemia Promielocítica Aguda/genética , Fenótipo , Transporte Proteico , Proteína SUMO-1/metabolismo , Telômero/genética , Telômero/metabolismo
6.
Nat Commun ; 10(1): 2491, 2019 06 06.
Artigo em Inglês | MEDLINE | ID: mdl-31171785

RESUMO

Genetic factors underlying leukocyte telomere length (LTL) may provide insights into telomere homeostasis, with direct links to disease susceptibility. Genetic evaluation of 23,096 Singaporean Chinese samples identifies 10 genome-wide loci (P < 5 × 10-8). Several of these contain candidate genes (TINF2, PARP1, TERF1, ATM and POT1) with potential roles in telomere biology and DNA repair mechanisms. Meta-analyses with additional 37,505 European individuals reveals six more genome-wide loci, including associations at MPHOSPH6, NKX2-3 and TYMS. We demonstrate that longer LTL associates with protection against respiratory disease mortality [HR = 0.854(0.804-0.906), P = 1.88 × 10-7] in the Singaporean Chinese samples. We further show that the LTL reducing SNP rs7253490 associates with respiratory infections (P = 7.44 × 10-4) although this effect may not be strongly mediated through LTL. Our data expands on the genetic basis of LTL and may indicate on a potential role of LTL in immune competence.


Assuntos
Grupo com Ancestrais do Continente Asiático/genética , Reparo do DNA/genética , Leucócitos/metabolismo , Homeostase do Telômero/genética , Telômero/metabolismo , Adulto , Idoso , Idoso de 80 Anos ou mais , Estudos de Coortes , Grupo com Ancestrais do Continente Europeu/genética , Feminino , Estudo de Associação Genômica Ampla , Humanos , Masculino , Pessoa de Meia-Idade , Estudos Prospectivos , Infecções Respiratórias/genética , Singapura , Adulto Jovem
7.
Chemistry ; 25(47): 11085-11097, 2019 Aug 22.
Artigo em Inglês | MEDLINE | ID: mdl-31219221

RESUMO

Naphthalene diimide (NDI) dyads exhibiting a different substitution pattern and linker length have been synthesised and evaluated as G-quadruplex (G4) ligands, by investigating their cytotoxicity in selected cell lines. The dyads with the long C7 linker exhibit extremely low IC50 values, below 10 nm, on different cancer cell lines. Contrary, the dyads with the shorter C4 linker were much less effective, with IC values increasing up to 1 µm. Among the three dyads with the longest linker, small differences in the IC50 values emerge, suggesting that the linker length plays a more important role than the substitution pattern. We have further shown that the dyads are able to induce cellular DNA damage response, which is not limited to the telomeric regions and is likely the origin of their cytotoxicity. Both absorption titration and dynamic light scattering of the most cytotoxic dyads in the presence of hTel22 highlight their ability to induce effective G4 aggregation, acting as non-covalent cross-linking agents.


Assuntos
Dano ao DNA/efeitos dos fármacos , Reparo do DNA/efeitos dos fármacos , Quadruplex G , Imidas/farmacologia , Naftalenos/farmacologia , Linhagem Celular Tumoral , Proliferação de Células/efeitos dos fármacos , Ensaios de Seleção de Medicamentos Antitumorais , Humanos , Imidas/síntese química , Imidas/química , Ligantes , Metáfase/efeitos dos fármacos , Microscopia de Fluorescência , Naftalenos/síntese química , Naftalenos/química , Proteínas Proto-Oncogênicas c-kit/genética , Proteínas Proto-Oncogênicas c-kit/metabolismo , Proteínas Proto-Oncogênicas c-myc/genética , Proteínas Proto-Oncogênicas c-myc/metabolismo , Telômero/efeitos dos fármacos , Telômero/metabolismo
8.
Int J Mol Sci ; 20(11)2019 Jun 07.
Artigo em Inglês | MEDLINE | ID: mdl-31181625

RESUMO

Chromosome ends are transcribed into long noncoding telomeric repeat-containing RNA (TERRA) from subtelomeric promoters. A class of TERRA promoters are associated with CpG islands embedded in repetitive DNA tracts. Cytosines in these subtelomeric CpG islands are frequently methylated in telomerase-positive cancer cells, and demethylation induced by depletion of DNA methyltransferases is associated with increased TERRA levels. However, the direct evidence and the underlying mechanism regulating TERRA expression through subtelomeric CpG islands methylation are still to establish. To analyze TERRA regulation by subtelomeric DNA methylation in human cell line (HeLa), we used an epigenetic engineering tool based on CRISPR-dCas9 (clustered regularly interspaced short palindromic repeats - dead CRISPR associated protein 9) associated with TET1 (ten-eleven 1 hydroxylase) to specifically demethylate subtelomeric CpG islands. This targeted demethylation caused an up-regulation of TERRA, and the enhanced TERRA production depended on the methyl-sensitive transcription factor NRF1 (nuclear respiratory factor 1). Since AMPK (AMP-activated protein kinase) is a well-known activator of NRF1, we treated cells with an AMPK inhibitor (compound C). Surprisingly, compound C treatment increased TERRA levels but did not inhibit AMPK activity in these experimental conditions. Altogether, our results provide new insight in the fine-tuning of TERRA at specific subtelomeric promoters and could allow identifying new regulators of TERRA.


Assuntos
Metilação de DNA , Fator 1 Nuclear Respiratório/metabolismo , Telômero/genética , Ilhas de CpG , Epigênese Genética , Células HeLa , Humanos , Regiões Promotoras Genéticas , Proteínas Quinases/metabolismo , RNA Longo não Codificante/genética , RNA Longo não Codificante/metabolismo , Sequências Repetitivas de Ácido Nucleico/genética , Telômero/metabolismo
9.
Int J Mol Med ; 44(1): 218-226, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31115552

RESUMO

Telomeres are nucleotide tandem repeats located at the tip of eukaryotic chromosomes that maintain genomic integrity. The gradual shortening of telomeres leads to cellular senescence and apoptosis, a key mechanism of aging and age­related chronic diseases. Epigenetic factors, such as nutrition, exercise and tobacco can affect the rate at which telomeres shorten and can modify the risk of developing chronic diseases. In this study, we evaluated the effects of a combination of nutraceutical supplements (NS) on telomere length (TL) in healthy volunteers with no medical history of any disease. Participants (n=47) were selected from healthy outpatients visiting a private clinic and were divided into the experimental group (n=16), that received the NS and the control group (n=31). We estimated the length of single telomeres in metaphase spread leukocytes, isolated from peripheral blood, using quantitative­fluorescent in situ hybridization (Q­FISH) analysis. The length of the whole telomere genome was significantly increased (P<0.05) for the mean, 1st quartile and median measurements in the experimental group. Similar findings were observed for short TL (20th percentile) (P<0.05) for the median and 3rd quartile measurements in the NS group, compared to the control group. The beneficial effects of the supplements on the length of short telomeres remained significant (P<0.05) following adjustment for age and sex. Telomeres were moderately longer in female patients compared to the male patients. On the whole, the findings of this study suggest that the administration of NS may be linked to sustaining the TL.


Assuntos
Suplementos Nutricionais , Leucócitos/metabolismo , Caracteres Sexuais , Homeostase do Telômero/efeitos dos fármacos , Telômero/metabolismo , Adulto , Feminino , Humanos , Masculino , Pessoa de Meia-Idade
10.
Adv Clin Chem ; 90: 81-132, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31122612

RESUMO

Ever since their discovery, the telomeres and the telomerase have been topics of intensive research, first as a mechanism of cellular aging and later as an indicator of health and diseases in humans. By protecting the chromosome ends, the telomeres play a vital role in preserving the information in our genome. Telomeres shorten with age and the rate of telomere erosion provides insight into the proliferation history of cells. The pace of telomere attrition is known to increase at the onset of several pathological conditions. Telomere shortening has been emerging as a potential contributor in the pathogenesis of several neurological disorders including autism spectrum disorders (ASD), schizophrenia, Alzheimer's disease (AD), Parkinson's disease (PD) and depression. The rate of telomere attrition in the brain is slower than that of other tissues owing to the low rate of cell proliferation in brain. Telomere maintenance is crucial for the functioning of stem cells in brain. Taking together the studies on telomere attrition in various neurological disorders, an association between telomere shortening and disease status has been demonstrated in schizophrenia, AD and depression, in spite of a few negative reports. But, studies in ASD and PD have failed to produce conclusive results. The cause-effect relationship between TL and neurological disorders is yet to be elucidated. The factors responsible for telomere erosion, which have also been implicated in the pathogenesis of neurological disorders, need to be explored in detail. Telomerase activation is now being considered as a potential therapeutic strategy for neurological disorders.


Assuntos
Doenças do Sistema Nervoso/genética , Telômero/genética , Telômero/metabolismo , Animais , Southern Blotting , Humanos , Hibridização in Situ Fluorescente , Reação em Cadeia da Polimerase
11.
Biomed Res Int ; 2019: 8327629, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31111068

RESUMO

Sleep deprivation and the consequent circadian clock disruption has become an emergent health question being associated with premature aging and earlier chronic diseases onset. Night-shift work leads to circadian clock misalignment, which is linked to several age-related diseases. However, mechanisms of this association are not well understood. Aim of this study is to explore in night-shift workers early indicators of oxidative stress response and biological aging [oxidized/methylated DNA bases and leukocytes telomere length (LTL)] and late indicators of functional aging [lung function measurements (FEV1 and FVC)] in relation to personal evaluation of work capacity, measured by work ability index (WAI). One hundred fifty-five hospital workers were studied within the framework of a cross-sectional study. We collected physiological, pathological, and occupational history including pack-years, alcohol consumption, physical activity, and night shifts, together with blood and urine samples. Relationships were appraised by univariate and multivariate ordered-logistic regression models. We found that workers with good and excellent WAI present higher FEV1 (p< 0.01) and number of night-work shifts (p<0.05), but they reveal higher urinary levels of 8-oxoGua (p<0.01) and shorter LTL (p<0.05). We confirmed that higher work ability was prevalent among chronological younger workers (p<0.05), who have also a significant reduced number of diseases, particularly chronic (p<0.01) and musculoskeletal diseases (p<0.01). The new findings which stem from our work are that subjects with the highest work ability perception may have more demanding and burdensome tasks; they in fact present the highest number of night-shift work and produce unbalanced oxidative stress response that might induce premature aging.


Assuntos
Estresse Oxidativo , Fenômenos Fisiológicos Respiratórios , Telômero/metabolismo , Tolerância ao Trabalho Programado/fisiologia , Tolerância ao Trabalho Programado/psicologia , Adolescente , Adulto , Idoso , Envelhecimento/fisiologia , Pessoal Técnico de Saúde , Relógios Biológicos , Ritmo Circadiano/fisiologia , Estudos Transversais , Metilação de DNA , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Análise Multivariada , Oxirredução , Análise de Regressão , Jornada de Trabalho em Turnos , Sono/fisiologia , Transtornos do Sono do Ritmo Circadiano/psicologia , Inquéritos e Questionários , Adulto Jovem
12.
Nat Commun ; 10(1): 2253, 2019 05 28.
Artigo em Inglês | MEDLINE | ID: mdl-31138795

RESUMO

Telomerase negative immortal cancer cells elongate telomeres through the Alternative Lengthening of Telomeres (ALT) pathway. While sustained telomeric replicative stress is required to maintain ALT, it might also lead to cell death when excessive. Here, we show that the ATPase/translocase activity of FANCM keeps telomeric replicative stress in check specifically in ALT cells. When FANCM is depleted in ALT cells, telomeres become dysfunctional, and cells stop proliferating and die. FANCM depletion also increases ALT-associated marks and de novo synthesis of telomeric DNA. Depletion of the BLM helicase reduces the telomeric replication stress and cell proliferation defects induced by FANCM inactivation. Finally, FANCM unwinds telomeric R-loops in vitro and suppresses their accumulation in cells. Overexpression of RNaseH1 completely abolishes the replication stress remaining in cells codepleted for FANCM and BLM. Thus, FANCM allows controlled ALT activity and ALT cell proliferation by limiting the toxicity of uncontrolled BLM and telomeric R-loops.


Assuntos
DNA Helicases/genética , Replicação do DNA/genética , RecQ Helicases/genética , Homeostase do Telômero/genética , Telômero/metabolismo , Morte Celular/genética , Linhagem Celular Tumoral , Proliferação de Células/genética , DNA Helicases/metabolismo , Células HEK293 , Células HeLa , Humanos , RecQ Helicases/metabolismo , Ribonuclease H/genética , Ribonuclease H/metabolismo
13.
Nat Commun ; 10(1): 2252, 2019 05 28.
Artigo em Inglês | MEDLINE | ID: mdl-31138797

RESUMO

The collapse of stalled replication forks is a major driver of genomic instability. Several committed mechanisms exist to resolve replication stress. These pathways are particularly pertinent at telomeres. Cancer cells that use Alternative Lengthening of Telomeres (ALT) display heightened levels of telomere-specific replication stress, and co-opt stalled replication forks as substrates for break-induced telomere synthesis. FANCM is a DNA translocase that can form independent functional interactions with the BLM-TOP3A-RMI (BTR) complex and the Fanconi anemia (FA) core complex. Here, we demonstrate that FANCM depletion provokes ALT activity, evident by increased break-induced telomere synthesis, and the induction of ALT biomarkers. FANCM-mediated attenuation of ALT requires its inherent DNA translocase activity and interaction with the BTR complex, but does not require the FA core complex, indicative of FANCM functioning to restrain excessive ALT activity by ameliorating replication stress at telomeres. Synthetic inhibition of FANCM-BTR complex formation is selectively toxic to ALT cancer cells.


Assuntos
Proteínas de Transporte/metabolismo , DNA Helicases/metabolismo , DNA Topoisomerases Tipo I/metabolismo , Proteínas de Ligação a DNA/metabolismo , Neoplasias/metabolismo , Proteínas Nucleares/metabolismo , RecQ Helicases/metabolismo , Homeostase do Telômero , Telômero/metabolismo , Linhagem Celular Tumoral , Replicação do DNA , Células HCT116 , Células HEK293 , Células HeLa , Humanos
14.
Mol Biol (Mosk) ; 53(2): 268-273, 2019.
Artigo em Russo | MEDLINE | ID: mdl-31099776

RESUMO

Many human genes that control human embryonic development and differentiation of human cells form chromosomal contact with rRNA gene clusters, which are involved in the epigenetic regulation of many genes. The sites of rRNA gene contact often fall on extended (up to 50 kb) regions containing a chromatin mark, H3K27ac histone, typical for superenhancers, as well as on pericentromeric and subtelomeric regions of chromosomes. We found that the DUX4 genes located in the subtelomeric region of human chromosome 4 are surrounded by regions that are often in contact with the rRNA genes. The 25 kb region of this chromosome, presented in version hg19 of the sequenced human genome, contains several copies of the DUX4 gene. The sites of rRNA gene contacts located around this region contain methylation sites as well as CTCF binding sites. It is assumed that the rRNA gene contacts are important in silencing these DUX4 gene copies.


Assuntos
DNA Ribossômico/genética , Desenvolvimento Embrionário/genética , Proteínas de Homeodomínio/genética , Família Multigênica/genética , Fator de Ligação a CCCTC/metabolismo , Cromatina/genética , Cromatina/metabolismo , Cromossomos Humanos Par 4/genética , Epigênese Genética , Histonas/química , Histonas/metabolismo , Humanos , Telômero/genética , Telômero/metabolismo
15.
Molecules ; 24(8)2019 Apr 22.
Artigo em Inglês | MEDLINE | ID: mdl-31013622

RESUMO

G-quadruplex (G4) DNA secondary structures formed in human telomeres have been shown to inhibit cancer-specific telomerase and alternative lengthening of telomere (ALT) pathways. Thus, human telomeric G-quadruplexes are considered attractive targets for anticancer drugs. Human telomeric G-quadruplexes are structurally polymorphic and predominantly form two hybrid-type G-quadruplexes, namely hybrid-1 and hybrid-2, under physiologically relevant solution conditions. To date, only a handful solution structures are available for drug complexes of human telomeric G-quadruplexes. In this review, we will describe two recent solution structural studies from our labs. We use NMR spectroscopy to elucidate the solution structure of a 1:1 complex between a small molecule epiberberine and the hybrid-2 telomeric G-quadruplex, and the structures of 1:1 and 4:2 complexes between a small molecule Pt-tripod and the hybrid-1 telomeric G-quadruplex. Structural information of small molecule complexes can provide important information for understanding small molecule recognition of human telomeric G-quadruplexes and for structure-based rational drug design targeting human telomeric G-quadruplexes.


Assuntos
Quadruplex G , Proteínas de Neoplasias/química , Telomerase/química , Homeostase do Telômero , Telômero/química , Humanos , Proteínas de Neoplasias/antagonistas & inibidores , Proteínas de Neoplasias/metabolismo , Ressonância Magnética Nuclear Biomolecular , Telomerase/antagonistas & inibidores , Telomerase/metabolismo , Telômero/metabolismo
16.
Nucleic Acids Res ; 47(10): 5368-5380, 2019 06 04.
Artigo em Inglês | MEDLINE | ID: mdl-30931479

RESUMO

The telomerase holoenzyme responsible for maintaining telomeres in vertebrates requires many components in vivo, including dyskerin. Dyskerin binds and regulates the accumulation of the human telomerase RNA, hTR, as well as other non-coding RNAs that share the conserved H/ACA box motif. The precise mechanism by which dyskerin controls hTR levels is unknown, but is evidenced by defective hTR accumulation caused by substitutions in dyskerin, that are observed in the X-linked telomere biology disorder dyskeratosis congenita (X-DC). To understand the role of dyskerin in hTR accumulation, we analyzed X-DC substitutions K39E and K43E in the poorly characterized dyskerin N-terminus, and A353V within the canonical RNA binding domain (the PUA). These variants exhibited impaired binding to hTR and polyadenylated hTR species, while interactions with other H/ACA RNAs appear largely unperturbed by the N-terminal substitutions. hTR accumulation and telomerase activity defects of dyskerin-deficient cells were rescued by wildtype dyskerin but not the variants. hTR 3' extended or polyadenylated species did not accumulate, suggesting hTR precursor degradation occurs upstream of mature complex assembly in the absence of dyskerin binding. Our findings demonstrate that the dyskerin-hTR interaction mediated by PUA and N-terminal residues of dyskerin is crucial to prevent unchecked hTR degradation.


Assuntos
Proteínas de Ciclo Celular/metabolismo , Proteínas Nucleares/metabolismo , Estabilidade de RNA , RNA/genética , Telomerase/metabolismo , Motivos de Aminoácidos , Proteínas de Ciclo Celular/genética , Núcleo Celular/metabolismo , Citosol/metabolismo , Disceratose Congênita/genética , Células HEK293 , Humanos , Mutação , Proteínas Nucleares/genética , Domínios Proteicos , RNA Interferente Pequeno/metabolismo , Proteínas de Ligação a RNA/metabolismo , Telomerase/genética , Telômero/metabolismo
17.
Nucleic Acids Res ; 47(11): 5684-5697, 2019 06 20.
Artigo em Inglês | MEDLINE | ID: mdl-30937455

RESUMO

KEOPS complex is one of the most conserved protein complexes in eukaryotes. It plays important roles in both telomere uncapping and tRNA N6-threonylcarbamoyladenosine (t6A) modification in budding yeast. But whether KEOPS complex plays any roles in DNA repair remains unknown. Here, we show that KEOPS complex plays positive roles in both DNA damage response and homologous recombination-mediated DNA repair independently of its t6A synthesis function. Additionally, KEOPS displays DNA binding activity in vitro, and is recruited to the chromatin at DNA breaks in vivo, suggesting a direct role of KEOPS in DSB repair. Mechanistically, KEOPS complex appears to promote DNA end resection through facilitating the association of Exo1 and Dna2 with DNA breaks. Interestingly, inactivation of both KEOPS and Mre11/Rad50/Xrs2 (MRX) complexes results in synergistic defect in DNA resection, revealing that KEOPS and MRX have some redundant functions in DNA resection. Thus we uncover a t6A-independent role of KEOPS complex in DNA resection, and propose that KEOPS might be a DSB sensor to assist cells in maintaining chromosome stability.


Assuntos
DNA Helicases/fisiologia , DNA Fúngico , Exodesoxirribonucleases/fisiologia , Recombinação Homóloga , Reparo de DNA por Recombinação , Proteínas de Saccharomyces cerevisiae/fisiologia , Ligação Competitiva , Cromatina/química , DNA/química , Quebras de DNA de Cadeia Dupla , Reparo do DNA , Proteínas de Ligação a DNA/metabolismo , Endodesoxirribonucleases/metabolismo , Exodesoxirribonucleases/metabolismo , Metaloendopeptidases/metabolismo , Mutação , Ligação Proteica , Proteínas Serina-Treonina Quinases/metabolismo , Saccharomyces cerevisiae/genética , Proteínas de Saccharomyces cerevisiae/metabolismo , Telômero/metabolismo , Fatores de Transcrição/metabolismo
18.
Phys Biol ; 16(4): 046005, 2019 05 07.
Artigo em Inglês | MEDLINE | ID: mdl-30943453

RESUMO

Meiotic homolog pairing involves associations between homologous DNA regions scattered along the length of a chromosome. When homologs associate, they tend to do so by a processive zippering process, which apparently results from avidity effects. Using a computational model, we show that this avidity-driven processive zippering reduces the selectivity of pairing. When active random forces are applied to telomeres, this drop in selectivity is eliminated in a force-dependent manner. Further simulations suggest that active telomere forces are engaged in a tug-of-war against zippering, which can be interpreted as a Brownian ratchet with a stall force that depends on the dissociation constant of pairing. When perfectly homologous regions of high affinity compete with homeologous regions of lower affinity, the affinity difference can be amplified through this tug of war effect provided the telomere force acts in a range that is strong enough to oppose zippering of homeologs while still permitting zippering of correct homologs. The degree of unzippering depends on the radius of the nucleus, such that complete unzippering of homeologous regions can only take place if the nucleus is large enough to pull the two chromosomes completely apart. A picture of meiotic pairing thus emerges that is fundamentally mechanical in nature, possibly explaining the purpose of active telomere forces, increased nuclear diameter, and the presence of 'Maverick' chromosomes in meiosis.


Assuntos
Pareamento Cromossômico/fisiologia , Simulação por Computador , Modelos Biológicos , Telômero/metabolismo , Fenômenos Biofísicos , Cromossomos/metabolismo , Meiose/fisiologia , Termodinâmica
19.
Depress Anxiety ; 36(6): 565-575, 2019 06.
Artigo em Inglês | MEDLINE | ID: mdl-30958913

RESUMO

BACKGROUND: Telomeres cap and protect DNA but shorten with each somatic cell division. Aging and environmental and lifestyle factors contribute to the speed of telomere attrition. Current evidence suggests a link between relative telomere length (RTL) and depression but the directionality of the relationship remains unclear. We prospectively examined associations between RTL and subsequent depressive symptom trajectories. METHODS: Among 8,801 women of the Nurses' Health Study, depressive symptoms were measured every 4 years from 1992 to 2012; group-based trajectories of symptoms were identified using latent class growth-curve analysis. Multinomial logistic models were used to relate midlife RTLs to the probabilities of assignment to subsequent depressive symptom trajectory groups. RESULTS: We identified four depressive symptom trajectory groups: minimal depressive symptoms (62%), worsening depressive symptoms (14%), improving depressive symptoms (19%), and persistent-severe depressive symptoms (5%). Longer midlife RTLs were related to significantly lower odds of being in the worsening symptoms trajectory versus minimal trajectory but not to other trajectories. In comparison with being in the minimal symptoms group, the multivariable-adjusted odds ratio of being in the worsening depressive symptoms group was 0.78 (95% confidence interval, 0.62-0.97; p = 0.02), for every standard deviation increase in baseline RTL. CONCLUSIONS: In this large prospective study of generally healthy women, longer telomeres at midlife were associated with significantly lower risk of a subsequent trajectory of worsening mood symptoms over 20 years. The results raise the possibility of telomere shortening as a novel contributing factor to late-life depression.


Assuntos
Envelhecimento/genética , Envelhecimento/psicologia , Depressão/diagnóstico , Depressão/genética , Encurtamento do Telômero/fisiologia , Telômero/metabolismo , Adulto , Transtorno Depressivo/diagnóstico , Transtorno Depressivo/genética , Feminino , Humanos , Modelos Logísticos , Pessoa de Meia-Idade , Estudos Prospectivos , Fatores de Risco , Telômero/genética , Encurtamento do Telômero/genética
20.
Nucleic Acids Res ; 47(10): 5243-5259, 2019 06 04.
Artigo em Inglês | MEDLINE | ID: mdl-30976812

RESUMO

Human CST (CTC1-STN1-TEN1) is an RPA-like complex that associates with G-rich single-strand DNA and helps resolve replication problems both at telomeres and genome-wide. We previously showed that CST binds and disrupts G-quadruplex (G4) DNA in vitro, suggesting that CST may prevent in vivo blocks to replication by resolving G4 structures. Here, we demonstrate that CST binds and unfolds G4 with similar efficiency to RPA. In cells, CST is recruited to telomeric and non-telomeric chromatin upon G4 stabilization, even when ATR/ATM pathways were inhibited. STN1 depletion increases G4 accumulation and slows bulk genomic DNA replication. At telomeres, combined STN1 depletion and G4 stabilization causes multi-telomere FISH signals and telomere loss, hallmarks of deficient telomere duplex replication. Strand-specific telomere FISH indicates preferential loss of C-strand DNA while analysis of BrdU uptake during leading and lagging-strand telomere replication shows preferential under-replication of lagging telomeres. Together these results indicate a block to Okazaki fragment synthesis. Overall, our findings indicate a novel role for CST in maintaining genome integrity through resolution of G4 structures both ahead of the replication fork and on the lagging strand template.


Assuntos
Quadruplex G , Proteínas de Ligação a Telômeros/genética , Animais , Linhagem Celular , DNA , DNA Polimerase I/metabolismo , Replicação do DNA , DNA de Cadeia Simples/metabolismo , Transferência Ressonante de Energia de Fluorescência , Células HeLa , Humanos , Hibridização in Situ Fluorescente , Insetos , Cinética , Ligação Proteica , Telomerase/metabolismo , Telômero/metabolismo
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