Release of Telomeric DNA from Chromosomes in Immortal Human Cells Lacking Telomerase Activity

1998 ◽  
Vol 248 (2) ◽  
pp. 223-227 ◽  
Author(s):  
Hideki Ogino ◽  
Kazuhiko Nakabayashi ◽  
Mikio Suzuki ◽  
Ei-ichi Takahashi ◽  
Michihiko Fujii ◽  
...  
Keyword(s):  
Telomerase Activity ◽  
Human Cells ◽  
Telomeric Dna

scholarly journals Reprogramming of telomerase by expression of mutant telomerase RNA template in human cells leads to altered telomeres that correlate with reduced cell viability.

1997 ◽  
Vol 17 (11) ◽  
pp. 6394-6401 ◽  
Author(s):  
L Marusíc ◽  
M Anton ◽  
A Tidy ◽  
P Wang ◽  
B Villeponteau ◽  
...  
Keyword(s):  
Telomerase Activity ◽  
Human Cells ◽  
Proliferative Potential ◽  
Wild Type ◽  
Telomeric Dna ◽  
Wild Type Enzyme ◽  
Growth And Survival ◽  
Template Sequence ◽  
Human Telomerase ◽  
Neomycin Resistance

Telomerase synthesizes telomeric DNA by copying the template sequence of its own RNA component. In Tetrahymena thermophila and yeast (G. Yu, J. D. Bradley, L. D. Attardi, and E. H. Blackburn, Nature 344:126-131, 1990; M. McEachern and E. H. Blackburn, Nature 376:403-409, 1995), mutations in the template domain of this RNA result in synthesis of mutant telomeres and in impaired cell growth and survival. We have investigated whether mutant telomerase affects the proliferative potential and viability of immortal human cells. Plasmids encoding mutant or wild-type template RNAs (hTRs) of human telomerase and the neomycin resistance gene were transfected into human cells to generate stable transformants. Expression of mutant hTR resulted in the appearance of mutant telomerase activity and in the synthesis of mutant telomeres. Transformed cells were not visibly affected in their growth and viability when grown as mass populations. However, a reduction in plating efficiency and growth rate and an increase in the number of senescent cells were detected in populations with mutant telomeres by colony-forming assays. These results suggest that the presence of mutant telomerase, even if coexpressed with the wild-type enzyme, can be deleterious to cells, likely as a result of the impaired function of hybrid telomeres.

scholarly journals Telomerase activity is restored in human cells by ectopic expression of hTERT (hEST2), the catalytic subunit of telomerase

Oncogene ◽  
1998 ◽  
Vol 16 (9) ◽  
pp. 1217-1222 ◽  
Author(s):  
Christopher M Counter ◽  
Matthew Meyerson ◽  
Elinor Ng Eaton ◽  
Leif W Ellisen ◽  
Stephanie Dickinson Caddle ◽  
...  
Keyword(s):  
Ectopic Expression ◽  
Telomerase Activity ◽  
Human Cells ◽  
Catalytic Subunit

A hypomorphic allele of telomerase uncovers the minimal functional length of telomeres in Arabidopsis

Genetics ◽  
2021 ◽  
Author(s):  
J Matthew Watson ◽  
Johanna Trieb ◽  
Martina Troestl ◽  
Kyle Renfrew ◽  
Terezie Mandakova ◽  
...  
Keyword(s):  
Genome Stability ◽  
Telomerase Activity ◽  
Minimal Length ◽  
Proper Function ◽  
Loop Formation ◽  
Telomeric Dna ◽  
Essential Requirement ◽  
Cis Acting ◽  
Hypomorphic Allele ◽  
Necessary And Sufficient

Abstract Despite the essential requirement of telomeric DNA for genome stability, the length of telomere tracts between species substantially differs, raising the question of the minimal length of telomeric DNA necessary for proper function. Here we address this question using a hypomorphic allele of the telomerase catalytic subunit, TERT. We show that although this construct partially restored telomerase activity to a tert mutant, telomeres continued to shorten over several generations, ultimately stabilizing at a bimodal size distribution. Telomeres on two chromosome arms were maintained at a length of 1kb, while the remaining telomeres were maintained at 400 bp. The longest telomeres identified in this background were also significantly longer in wild type populations, suggesting cis-acting elements on these arms either promote telomerase processivity or recruitment. Genetically disrupting telomerase processivity in this background resulted in immediate lethality. Thus, telomeres of 400 bp are both necessary and sufficient for Arabidopsis viability. As this length is the estimated minimal length for t-loop formation, our data suggest that telomeres long enough to form a t-loop constitute the minimal functional length.

scholarly journals The conserved structure of plant telomerase RNA provides the missing link for an evolutionary pathway from ciliates to humans

2019 ◽  
Vol 116 (49) ◽  
pp. 24542-24550 ◽  
Author(s):  
Jiarui Song ◽  
Dhenugen Logeswaran ◽  
Claudia Castillo-González ◽  
Yang Li ◽  
Sreyashree Bose ◽  
...  
Keyword(s):  
Telomerase Activity ◽  
Telomere Maintenance ◽  
Telomerase Rna ◽  
Telomeric Dna ◽  
Structural Element ◽  
Stem Loop ◽  
Evolutionary Pathway ◽  
Pol Iii

Telomerase is essential for maintaining telomere integrity. Although telomerase function is widely conserved, the integral telomerase RNA (TR) that provides a template for telomeric DNA synthesis has diverged dramatically. Nevertheless, TR molecules retain 2 highly conserved structural domains critical for catalysis: a template-proximal pseudoknot (PK) structure and a downstream stem-loop structure. Here we introduce the authentic TR from the plant Arabidopsis thaliana, called AtTR, identified through next-generation sequencing of RNAs copurifying with Arabidopsis TERT. This RNA is distinct from the RNA previously described as the templating telomerase RNA, AtTER1. AtTR is a 268-nt Pol III transcript necessary for telomere maintenance in vivo and sufficient with TERT to reconstitute telomerase activity in vitro. Bioinformatics analysis identified 85 AtTR orthologs from 3 major clades of plants: angiosperms, gymnosperms, and lycophytes. Through phylogenetic comparisons, a secondary structure model conserved among plant TRs was inferred and verified using in vitro and in vivo chemical probing. The conserved plant TR structure contains a template-PK core domain enclosed by a P1 stem and a 3′ long-stem P4/5/6, both of which resemble a corresponding structural element in ciliate and vertebrate TRs. However, the plant TR contains additional stems and linkers within the template-PK core, allowing for expansion of PK structure from the simple PK in the smaller ciliate TR during evolution. Thus, the plant TR provides an evolutionary bridge that unites the disparate structures of previously characterized TRs from ciliates and vertebrates.

Telomeres, telomerase, and apoptosis

2004 ◽  
Vol 82 (4) ◽  
pp. 498-507 ◽  
Author(s):  
Chiara Mondello ◽  
A Ivana Scovassi
Keyword(s):  
Cancer Cells ◽  
Telomerase Activity ◽  
Telomeric Dna ◽  
Apoptotic Response ◽  
Reverse Transcriptase Enzyme ◽  
Limited Life ◽  
Specific Proteins ◽  
Telomere Capping ◽  
The Impact ◽  
High Order Chromatin

Telomeres are specialized high-order chromatin structures that cap the ends of eukaryotic chromosomes. In vertebrates, telomeric DNA is composed of repetitions of the TTAGGG hexanucleotide, is bound to a set of specific proteins, and is elongated by the reverse transcriptase enzyme telomerase. Telomerase activity is promptly detected in cells with an indefinite replicative potential, such as cancer cells, while is almost undetectable in normal cells, which are characterized by a limited life span. Mounting evidence indicates that the maintenance of telomere integrity and telomerase protect cells from apoptosis. Disruption of the telomere capping function and (or) telomerase inhibition elicit an apoptotic response in cancer cells, while restoration of telomerase activity in somatic cells confers resistance to apoptosis. The possible mechanisms linking telomeres, telomerase and apoptosis are discussed in this review, together with the impact of this field in anticancer research.Key words: telomeres, telomerase, telomeric proteins, apoptosis, tumorigenesis.

scholarly journals TIN2 Functions with TPP1/POT1 To Stimulate Telomerase Processivity

2019 ◽  
Vol 39 (21) ◽  
Author(s):  
Alexandra M. Pike ◽  
Margaret A. Strong ◽  
John Paul T. Ouyang ◽  
Carol W. Greider
Keyword(s):  
Telomere Length ◽  
Telomerase Activity ◽  
Human Cells ◽  
Short Telomere ◽  
Gene Encoding ◽  
Important Regulator

ABSTRACT TIN2 is an important regulator of telomere length, and mutations in TINF2, the gene encoding TIN2, cause short-telomere syndromes. While the genetics underscore the importance of TIN2, the mechanism through which TIN2 regulates telomere length remains unclear. Here, we tested the effects of human TIN2 on telomerase activity. We identified a new isoform in human cells, TIN2M, that is expressed at levels similar to those of previously studied TIN2 isoforms. All three TIN2 isoforms localized to and maintained telomere integrity in vivo, and localization was not disrupted by telomere syndrome mutations. Using direct telomerase activity assays, we discovered that TIN2 stimulated telomerase processivity in vitro. All of the TIN2 isoforms stimulated telomerase to similar extents. Mutations in the TPP1 TEL patch abrogated this stimulation, suggesting that TIN2 functions with TPP1/POT1 to stimulate telomerase processivity. We conclude from our data and previously published work that TIN2/TPP1/POT1 is a functional shelterin subcomplex.

scholarly journals Telomere length: how the length makes a difference

2020 ◽  
Vol 47 (9) ◽  
pp. 7181-7188 ◽  
Author(s):  
M. Lulkiewicz ◽  
J. Bajsert ◽  
P. Kopczynski ◽  
W. Barczak ◽  
B. Rubis
Keyword(s):  
Telomere Length ◽  
Meta Analysis ◽  
Telomerase Activity ◽  
Human Cells ◽  
Attrition Rate ◽  
Severe Damage ◽  
Telomere Attrition ◽  
Adult Men ◽  
Cell Life ◽  
Real Value

Abstract Telomerase is perceived as an immortality enzyme that might provide longevity to cells and whole organisms. Importantly, it is generally inactive in most somatic cells of healthy, adult men. Consequently, its substrates, i.e. telomeres, get shorter in most human cells with time. Noteworthy, cell life limitation due to telomere attrition during cell divisions, may not be as bad as it looks since longer cell life means longer exposition to harmful factors. Consequently, telomere length (attrition rate) becomes a factor that is responsible for inducing the signaling that leads to the elimination of cells that lived long enough to acquire severe damage. It seems that telomere length that depends on many different factors (including telomerase activity but also genetic factors, a hormonal profile that reflects sex, etc.) might become a useful marker of aging and exposition to stress. Thus in the current paper, we review the factors that affect telomere length in human cells focusing on sex that all together with different environmental and hormonal regulations as well as parental aspect affect telomere attrition rate. We also raise some limitations in the assessment of telomere length that hinders a trustworthy meta-analysis that might lead to acknowledgment of the real value of this parameter.

scholarly journals Lack of cell cycle regulation of telomerase activity in human cells

1997 ◽  
Vol 94 (20) ◽  
pp. 10687-10692 ◽  
Author(s):  
S. E. Holt ◽  
D. L. Aisner ◽  
J. W. Shay ◽  
W. E. Wright
Keyword(s):  
Cell Cycle ◽  
Cell Cycle Regulation ◽  
Telomerase Activity ◽  
Human Cells ◽  
Cycle Regulation

scholarly journals Yeast Est2p Affects Telomere Length by Influencing Association of Rap1p with Telomeric Chromatin

2008 ◽  
Vol 28 (7) ◽  
pp. 2380-2390 ◽  
Author(s):  
Hong Ji ◽  
Christopher J. Adkins ◽  
Bethany R. Cartwright ◽  
Katherine L. Friedman
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Telomere Length ◽  
Specific Binding ◽  
Telomerase Activity ◽  
Negative Regulator ◽  
Wild Type ◽  
Telomeric Dna ◽  
Telomere Length Homeostasis

ABSTRACT In Saccharomyces cerevisiae, the sequence-specific binding of the negative regulator Rap1p provides a mechanism to measure telomere length: as the telomere length increases, the binding of additional Rap1p inhibits telomerase activity in cis. We provide evidence that the association of Rap1p with telomeric DNA in vivo occurs in part by sequence-independent mechanisms. Specific mutations in EST2 (est2-LT) reduce the association of Rap1p with telomeric DNA in vivo. As a result, telomeres are abnormally long yet bind an amount of Rap1p equivalent to that observed at wild-type telomeres. This behavior contrasts with that of a second mutation in EST2 (est2-up34) that increases bound Rap1p as expected for a strain with long telomeres. Telomere sequences are subtly altered in est2-LT strains, but similar changes in est2-up34 telomeres suggest that sequence abnormalities are a consequence, not a cause, of overelongation. Indeed, est2-LT telomeres bind Rap1p indistinguishably from the wild type in vitro. Taken together, these results suggest that Est2p can directly or indirectly influence the binding of Rap1p to telomeric DNA, implicating telomerase in roles both upstream and downstream of Rap1p in telomere length homeostasis.

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