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Telomere and telomerase

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https://www.readbyqxmd.com/read/28334750/ctc1-mediated-c-strand-fill-in-is-an-essential-step-in-telomere-length-maintenance
#1
Xuyang Feng, Shih-Jui Hsu, Christopher Kasbek, Mary Chaiken, Carolyn M Price
To prevent progressive telomere shortening as a result of conventional DNA replication, new telomeric DNA must be added onto the chromosome end. The de novo DNA synthesis involves elongation of the G-rich strand of the telomere by telomerase. In human cells, the CST complex (CTC1-STN1-TEN1) also functions in telomere replication. CST first aids in duplication of the telomeric dsDNA. Then after telomerase has extended the G-rich strand, CST facilitates fill-in synthesis of the complementary C-strand. Here, we analyze telomere structure after disruption of human CTC1 and demonstrate that functional CST is essential for telomere length maintenance due to its role in mediating C-strand fill-in...
February 23, 2017: Nucleic Acids Research
https://www.readbyqxmd.com/read/28330934/fundamental-mechanisms-of-telomerase-action-in-yeasts-and-mammals-understanding-telomeres-and-telomerase-in-cancer-cells
#2
REVIEW
Christine A Armstrong, Kazunori Tomita
Aberrant activation of telomerase occurs in 85-90% of all cancers and underpins the ability of cancer cells to bypass their proliferative limit, rendering them immortal. The activity of telomerase is tightly controlled at multiple levels, from transcriptional regulation of the telomerase components to holoenzyme biogenesis and recruitment to the telomere, and finally activation and processivity. However, studies using cancer cell lines and other model systems have begun to reveal features of telomeres and telomerase that are unique to cancer...
March 2017: Open Biology
https://www.readbyqxmd.com/read/28324509/human-telomeric-g-quadruplex-structures-and-g-quadruplex-interactive-compounds
#3
Clement Lin, Danzhou Yang
G-quadruplexes are noncanonical secondary structures formed in DNA sequences containing consecutive runs of guanines. It has been shown that the 3' G-rich single-stranded overhangs of human telomeres can form G-quadruplex structures, and the human telomeric DNA G-quadruplexes are considered attractive targets for anticancer drugs. G-quadruplex-interactive compounds have been shown to inhibit telomerase access as well as telomere capping. Nuclear magnetic resonance (NMR) spectroscopy is a powerful method in determining the G-quadruplex structures under physiologically relevant conditions...
2017: Methods in Molecular Biology
https://www.readbyqxmd.com/read/28324508/in-vitro-preparation-and-crystallization-of-vertebrate-telomerase-subunits
#4
Jing Huang, Christopher J Bley, Dustin P Rand, Julian J L Chen, Ming Lei
Telomerase is a unique reverse transcriptase that replicates the telomeric DNA at most eukaryotic chromosomal ends. The telomerase consists of the catalytic protein subunit TERT and the RNA component TR that provides the template for telomeric DNA synthesis. In vitro reconstitution of telomerase core components in large quantity is the prerequisite to studying the catalytic mechanisms of telomerase at the structural level; however, large-scale preparation of recombinant telomerase, especially that of higher eukaryotes, has been a big challenge for a long time...
2017: Methods in Molecular Biology
https://www.readbyqxmd.com/read/28324504/cytogenetic-analysis-of-telomere-dysfunction
#5
Rekha Rai, Asha S Multani, Sandy Chang
Dysfunctional telomeres arising either through natural attrition due to telomerase deficiency or by the removal of telomere-binding proteins are recognized as double-stranded breaks (DSBs). Repair of DSBs is crucial for the maintenance of genome stability. In mammals, DSBs are repaired by either error-prone nonhomologous end joining (NHEJ) or error-free homologous recombination (HR) and can be visualized as chromosomal fusions.
2017: Methods in Molecular Biology
https://www.readbyqxmd.com/read/28324503/visualization-of-human-telomerase-localization-by-fluorescence-microscopy-techniques
#6
Eladio Abreu, Rebecca M Terns, Michael P Terns
Human telomerase is a ribonucleoprotein (RNP) that synthesizes DNA repeats at the ends of chromosomes and maintains telomere length and genome stability. The enzyme is comprised of telomerase RNA (hTR) (which provides the template for telomere addition) and several protein subunits including telomerase reverse transcriptase (hTERT) (the catalytic component). Intracellular trafficking of the enzyme has emerged as an important factor in the regulation of telomerase activity. Telomerase trafficking between nuclear Cajal bodies (proposed sites of telomerase biogenesis and regulation) and telomeres (sites of action) is regulated by the cell cycle in concordance with telomere synthesis during S phase...
2017: Methods in Molecular Biology
https://www.readbyqxmd.com/read/28324501/assessing-telomerase-activities-in-mammalian-cells-using-the-quantitative-pcr-based-telomeric-repeat-amplification-protocol-qtrap
#7
Shuai Jiang, Mengfan Tang, Huawei Xin, Junjiu Huang
Telomerase expression and activity appear elevated in >80% of human cancers. The activity of the telomerase may serve as a diagnostic marker for malignancy, and an indicator of the proliferative potential of somatic and stem cells. The telomeric repeat amplification protocol (TRAP) is a sensitive and accurate PCR-based assay for telomerase detection and measurement. Here, we describe a quantitative PCR-based TRAP assay (qTRAP) that is more convenient and amenable to high-throughput applications compared to traditional gel-based TRAP assays...
2017: Methods in Molecular Biology
https://www.readbyqxmd.com/read/28324500/analysis-of-yeast-telomerase-by-primer-extension-assays
#8
Min Hsu, Neal F Lue
Telomeres are specialized nucleoprotein structures located at eukaryotic chromosomal termini, which are required for chromosome stability and are maintained by a reverse transcriptase named telomerase. Budding yeast has served as an extremely useful model system for analyzing telomere maintenance because the organism offers a wide range of genetic and biochemical tools. Several milestones in telomerase research have been reached through investigation of the yeast system. For example, the consequence of telomerase loss was first characterized in the budding yeast Saccharomyces cerevisiae...
2017: Methods in Molecular Biology
https://www.readbyqxmd.com/read/28324499/telomere-terminal-g-c-strand-synthesis-measuring-telomerase-action-and-c-rich-fill-in
#9
Yong Zhao, Jerry W Shay, Woodring E Wright
Telomerase is present in most human cancers, and proliferative stem cells including germline cells. Telomerase plays an essential role in tumorigenesis by maintaining/elongating telomeric DNA, and thus preventing the telomere shortening that results in replicative senescence. Understanding telomerase action in vivo has important implication for both cancer and aging, but there are not robust methods for monitoring telomerase action. By combining a series of cell biological and biochemical approaches, and taking advantage of the enzyme DSN that specifically cuts double-stranded DNA and releases the telomeric overhangs, we have developed a method to monitor telomerase action during one cell cycle...
2017: Methods in Molecular Biology
https://www.readbyqxmd.com/read/28324497/telomere-g-rich-overhang-length-measurement-dsn-method
#10
Yong Zhao, Jerry W Shay, Woodring E Wright
Telomeres terminate in 3' single-stranded G-rich overhangs that function in telomere end protection and telomerase action. An accurate measurement of overhang length is challenging due to the presence of many kilobases of double-stranded telomere DNA. Here, a simple method is described that utilizes duplex specific nuclease (DSN) to digest all double-stranded DNA including telomeres to fragments of <10 bp, leaving the single-stranded overhangs intact. Their length can then be determined by Southern blot using super-sensitive telomere C-rich probes...
2017: Methods in Molecular Biology
https://www.readbyqxmd.com/read/28324494/analysis-of-average-telomere-length-in-human-telomeric-protein-knockout-cells-generated-by-crispr-cas9
#11
Jun Xu, Zhou Songyang, Dan Liu, Hyeung Kim
Telomeres play an important role in ensuring the integrity of the genome. Telomere shortening can lead to loss of genetic information and trigger DNA damage responses. Cultured mammalian cells have served as critical model systems for studying the function of telomere binding proteins and telomerase. Tremendous heterogeneity can be observed both between species and within a single cell population. Recent advances in genome editing (such as the development of the CRISPR/Cas9 platform) have further enabled researchers to carry out loss-of-function analysis of how disrupting key players in telomere maintenance affects telomere length regulation...
2017: Methods in Molecular Biology
https://www.readbyqxmd.com/read/28324493/introduction-to-telomeres-and-telomerase
#12
Zhou Songyang
Telomeres are ends of chromosomes that play an important part in the biology of eukaryotic cells. Continued optimization and development of technologies have enabled researchers to probe the mechanisms of telomere maintenance in ever expanding areas. A combination of molecular, genetic, proteomic, and biochemical approaches has revealed the complex and coordinated action of telomerase and telomere-associated proteins. The length and integrity of telomeres are maintained to prevent telomere dysfunction, which has been linked to senescence, aging, disease, and cancer...
2017: Methods in Molecular Biology
https://www.readbyqxmd.com/read/28320284/apoptotic-endonuclease-endog-inhibits-telomerase-activity-and-induces-malignant-transformation-of-human-cd4-t-cells
#13
D A Vasina, D D Zhdanov, E V Orlova, V S Orlova, M V Pokrovskaya, S S Aleksandrova, N N Sokolov
Telomerase activity is regulated by an alternative splicing of mRNA of the telomerase catalytic subunit hTERT (human telomerase reverse transcriptase). Increased expression of the inactive spliced hTERT results in inhibition of telomerase activity. Little is known about the mechanism of hTERT mRNA alternative splicing. This study was aimed at determining the effect of an apoptotic endonuclease G (EndoG) on alternative splicing of hTERT and telomerase activity in CD4+ human T lymphocytes. Overexpression of EndoG in CD4+ T cells downregulated the expression of the active full-length hTERT variant and upregulated the inactive alternatively spliced variant...
January 2017: Biochemistry. Biokhimii︠a︡
https://www.readbyqxmd.com/read/28303901/mutual-reinforcement-between-telomere-capping-and-canonical-wnt-signalling-in-the-intestinal-stem-cell-niche
#14
Ting-Lin B Yang, Qijun Chen, Jennifer T Deng, Geetha Jagannathan, John W Tobias, David C Schultz, Shan Wang, Christopher J Lengner, Anil K Rustgi, John P Lynch, F Brad Johnson
Critical telomere shortening (for example, secondary to partial telomerase deficiency in the rare disease dyskeratosis congenita) causes tissue pathology, but underlying mechanisms are not fully understood. Mice lacking telomerase (for example, mTR(-/-) telomerase RNA template mutants) provide a model for investigating pathogenesis. In such mice, after several generations of telomerase deficiency telomeres shorten to the point of uncapping, causing defects most pronounced in high-turnover tissues including intestinal epithelium...
March 17, 2017: Nature Communications
https://www.readbyqxmd.com/read/28301767/progress-in-human-and-tetrahymena-telomerase-structure
#15
Henry Chan, Yaqiang Wang, Juli Feigon
Telomerase is an RNA-protein complex that extends the 3' ends of linear chromosomes, using a unique telomerase reverse transcriptase (TERT) and template in the telomerase RNA (TR), thereby helping to maintain genome integrity. TR assembles with TERT and species-specific proteins, and telomerase function in vivo requires interaction with telomere-associated proteins. Over the past two decades, structures of domains of TR and TERT as well as other telomerase- and telomere-interacting proteins have provided insights into telomerase function...
March 15, 2017: Annual Review of Biophysics
https://www.readbyqxmd.com/read/28301132/nuclear-shell-biopolymers-initiated-by-telomere-elongation-for-individual-cancer-cell-imaging-and-drug-delivery
#16
Zhen Zhang, Yuting Jiao, Mengting Zhu, Shusheng Zhang
Here, we propose a strategy for unique nuclear-shell biopolymers initiated by telomere elongation for telomerase activity detection and precise drug delivery to individual cancer cells. Telomerase-triggered DNA rolling-circle amplification (RCA) is used to assemble nuclear-shell biopolymers with signal molecules for selective cancer cell recognition and efficient drug delivery to targeted individual cells. This strategy not only should allow the creation of clustered 5-carboxyfluorescein (FAM)-fluorescence spots in response to human-telomerase activity in individual cancer cells but also could efficiently deliver drugs to reduce the undesired death of healthy cells...
March 24, 2017: Analytical Chemistry
https://www.readbyqxmd.com/read/28300824/association-between-the-telomerase-rs2736098_tt-genotype-and-a-lower-risk-of-chronic-hepatitis-b-and-cirrhosis-in-chinese-males
#17
Guanghui Cheng, Xiaotian Yuan, Fang Wang, Qing Sun, Qian Xin, Kailin Li, Chao Sun, Zhaomin Lin, Yun Luan, Yiteng Xu, Ping Li, Feng Kong, Dawei Xu
OBJECTIVES: Chronic hepatitis B (CHB) is caused by infection of hepatitis B virus (HBV) and liver cirrhosis (LC) is its most common complication. The accumulated evidence indicates a genetic context of HBV infection phenotypes. Here we determine a potential association of CHB/LC with the genetic variant of telomerase reverse transcriptase (TERT), a key player in aging including immune-senescence. METHODS: The study included 227 Chinese CHB patients and 315 sex/age-matched healthy controls...
March 16, 2017: Clinical and Translational Gastroenterology
https://www.readbyqxmd.com/read/28289249/control-of-cellular-aging-tissue-function-and-cancer-by-p53-downstream-of-telomeres
#18
Caitlin M Roake, Steven E Artandi
Telomeres, the nucleoprotein complex at the ends of eukaryotic chromosomes, perform an essential cellular role in part by preventing the chromosomal end from initiating a DNA-damage response. This function of telomeres can be compromised as telomeres erode either as a consequence of cell division in culture or as a normal part of cellular ageing in proliferative tissues. Telomere dysfunction in this context leads to DNA-damage signaling and activation of the tumor-suppressor protein p53, which then can prompt either cellular senescence or apoptosis...
March 13, 2017: Cold Spring Harbor Perspectives in Medicine
https://www.readbyqxmd.com/read/28288903/silencing-of-htert-blocks-growth-and-migration-of-anaplastic-thyroid-cancer-cells
#19
Valentina Maggisano, Marilena Celano, Giovanni Enrico Lombardo, Saverio Massimo Lepore, Marialuisa Sponziello, Francesca Rosignolo, Antonella Verrienti, Federica Baldan, Efisio Puxeddu, Cosimo Durante, Sebastiano Filetti, Giuseppe Damante, Diego Russo, Stefania Bulotta
Mutations in the hTERT promoter responsible for constitutive telomerase activity are the most frequent genetic alteration detected in anaplastic thyroid cancer (ATC), and proposed as diagnostic and prognostic biomarker in these tumours. In this study we analyzed hTERT expression in a series of human ATCs and investigated the effects of small-interfering RNA-mediated silencing of hTERT on viability and migration and invasive properties of three human ATC cell lines. Expression of hTERT mRNA resulted increased in 8/10 ATCs compared to normal thyroid tissues...
March 10, 2017: Molecular and Cellular Endocrinology
https://www.readbyqxmd.com/read/28281877/comprehensive-analysis-of-interaction-networks-of-telomerase-reverse-transcriptase-with-multiple-bioinformatic-approach-deep-mining-the-potential-functions-of-telomere-and-telomerase
#20
Chunyu Hou, Fei Wang, Xuewen Liu, Guangming Chang, Feng Wang, Xin Geng
Telomerase reverse transcriptase (TERT)is the protein component of telomerase complex. Evidence has accumulated showing that the non-telomeric functions of TERT are independent of telomere elongation. However, the mechanisms governing the interaction between TERT and its target genes are not revealed clear. The biological functions of TERT are not fully elucidated and have thus far been underestimated. To further explore these functions, we investigated TERT interaction networks using multiple bioinformatic databases, including BioGRID, STRING, DAVID, GeneCards, GeneMANIA, PANTHER, miRWalk, mirTarBase, miRNet, miRDB and TargetScan...
March 6, 2017: Rejuvenation Research
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