Impaired telomerase activity in human cells expressing GFP-Ku86 fusion proteins

2008 ◽  
Vol 122 (3-4) ◽  
pp. 326-335 ◽  
Author(s):  
C. Badie ◽  
R.J. Yáñez-Muñoz ◽  
C. Muller ◽  
B. Salles ◽  
A.C.G. Porter
Keyword(s):  
Fusion Proteins ◽  
Telomerase Activity ◽  
Human Cells

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

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 A translocation-defective telomerase with low levels of activity and processivity stabilizes short telomeres and confers immortalization

2013 ◽  
Vol 24 (9) ◽  
pp. 1469-1479 ◽  
Author(s):  
Yasmin D'Souza ◽  
Tsz Wai Chu ◽  
Chantal Autexier
Keyword(s):  
Dna Synthesis ◽  
Telomerase Activity ◽  
Human Cells ◽  
Telomerase Reverse Transcriptase ◽  
Wild Type ◽  
Telomeric Repeats ◽  
Telomeric Sequences ◽  
Telomere Function ◽  
Low Levels ◽  
Limited Lifespan

Short, repetitive, G-rich telomeric sequences are synthesized by telomerase, a ribonucleoprotein consisting of telomerase reverse transcriptase (TERT) and an integrally associated RNA. Human TERT (hTERT) can repetitively reverse transcribe its RNA template, acting processively to add multiple telomeric repeats onto the same substrate. We investigated whether certain threshold levels of telomerase activity and processivity are required to maintain telomere function and immortalize human cells with limited lifespan. We assessed hTERT variants with mutations in motifs implicated in processivity and interaction with DNA, namely the insertion in fingers domain (V791Y), and the E primer grip motif (W930F). hTERT-W930F and hTERT-V791Y reconstitute reduced levels of DNA synthesis and processivity compared with wild-type telomerase. Of interest, hTERT-W930F is more defective in translocation than hTERT-V791Y. Nonetheless, hTERT-W930F, but not hTERT-V791Y, immortalizes limited-lifespan human cells. Both hTERT-W930F– and hTERT-V791Y–expressing cells harbor short telomeres, measured as signal free ends (SFEs), yet SFEs persist only in hTERT-V791Y cells, which undergo apoptosis, likely as a consequence of a defect in recruitment of hTERT-V791Y to telomeres. Our study is the first to demonstrate that low levels of DNA synthesis—on the order of 20% of wild-type telomerase levels—and extension of as few as three telomeric repeats are sufficient to maintain functional telomeres and immortalize limited-lifespan human cells.

Salicylic acid inducible nucleocytoplasmic shuttling of NPR1 fusion proteins in human cells

2021 ◽  
Author(s):  
Fatemeh Sadeghi ◽  
Monish Kumar ◽  
Irfan N Bandey ◽  
Xiaoyang Li ◽  
Badrinath Roysam ◽  
...  
Keyword(s):  
Salicylic Acid ◽  
Fusion Proteins ◽  
Human Cells ◽  
Nucleocytoplasmic Shuttling

Regulation of telomerase activity in quiescent immortalized human cells

1998 ◽  
Vol 1442 (2-3) ◽  
pp. 120-126 ◽  
Author(s):  
Wolfram Klapper ◽  
Kumud K. Singh ◽  
Klaus Heidorn ◽  
Reza Parwaresch ◽  
Guido Krupp
Keyword(s):  
Telomerase Activity ◽  
Human Cells

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 Expression and regulation by interferon of a double-stranded-RNA-specific adenosine deaminase from human cells: evidence for two forms of the deaminase.

1995 ◽  
Vol 15 (10) ◽  
pp. 5376-5388 ◽  
Author(s):  
J B Patterson ◽  
C E Samuel
Keyword(s):  
Adenosine Deaminase ◽  
Fusion Proteins ◽  
Immunoblot Analysis ◽  
Binding Activity ◽  
Human Cells ◽  
Cell Fractionation ◽  
Double Stranded Rna ◽  
Nuclear Extracts ◽  
Dsrna Binding ◽  
Ifn Treatment

A 6,474-nucleotide human cDNA clone designated K88, which encodes double-stranded RNA (dsRNA)-specific adenosine deaminase, was isolated in a screen for interferon (IFN)-regulated cDNAs. Northern (RNA) blot analysis revealed that the K88 cDNA hybridized to a single major transcript of approximately 6.7 kb in human cells which was increased about fivefold by IFN treatment. Polyclonal antisera prepared against K88 cDNA products expressed in Escherichia coli as glutathione S-transferase (GST) fusion proteins recognized two proteins by Western (immunoblot) analysis. An IFN-induced 150-kDa protein and a constitutively expressed 110-kDa protein whose level was not altered by IFN treatment were detected in human amnion U and neuroblastoma SH-SY5Y cell lines. Only the 150-kDa protein was detected in mouse fibroblasts with antiserum raised against the recombinant human protein; the mouse 150-kDa protein was IFN inducible. Immunofluorescence microscopy and cell fractionation analyses showed that the 110-kDa protein was exclusively nuclear, whereas the 150-kDa protein was present in both the cytoplasm and nucleus of human cells. The amino acid sequence deduced from the K88 cDNA includes three copies of the highly conserved R motif commonly found in dsRNA-binding proteins. Both the 150-kDa and the 110-kDa proteins prepared from human nuclear extracts bound to double-stranded but not to single-stranded RNA affinity columns. Furthermore, E. coli-expressed GST-K88 fusion proteins that included the R motif possessed dsRNA-binding activity. Extracts prepared either from K88 cDNA-transfected cells or from IFN-treated cells contained increased dsRNA-specific adenosine deaminase enzyme activity. These results establish that K88 encodes an IFN-inducible dsRNA-specific adenosine deaminase and suggest that at least two forms of dsRNA-specific adenosine deaminase occur in human cells.

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