Normal telomere length and chromosomal end capping in poly(ADP-ribose) polymerase–deficient mice and primary cells despite increased chromosomal instability
TL;DR: The results presented here indicate that PARp-1 does not play a major role in regulating telomere length or in telomeric end capping, and the chromosomal instability of PARP-1−/− primary cells can be explained by the repair defect associated to PARP -1 deficiency.
Abstract: Poly(ADP-ribose) polymerase (PARP)-1, a detector of single-strand breaks, plays a key role in the cellular response to DNA damage. PARP-1-deficient mice are hypersensitive to genotoxic agents and display genomic instability due to a DNA repair defect in the base excision repair pathway. A previous report suggested that PARP-1-deficient mice also had a severe telomeric dysfunction consisting of telomere shortening and increased end-to-end fusions (d'Adda di Fagagna, F., M.P. Hande, W.-M. Tong, P.M. Lansdorp, Z.-Q. Wang, and S.P. Jackson. 1999. NAT: Genet. 23:76-80). In contrast to that, and using a panoply of techniques, including quantitative telomeric (Q)-FISH, we did not find significant differences in telomere length between wild-type and PARP-1(-/)- littermate mice or PARP-1(-/)- primary cells. Similarly, there were no differences in the length of the G-strand overhang. Q-FISH and spectral karyotyping analyses of primary PARP-1(-/)- cells showed a frequency of 2 end-to-end fusions per 100 metaphases, much lower than that described previously (d'Adda di Fagagna et al., 1999). This low frequency of end-to-end fusions in PARP-1(-/)- primary cells is accordant with the absence of severe proliferative defects in PARP-1(-/)- mice. The results presented here indicate that PARP-1 does not play a major role in regulating telomere length or in telomeric end capping, and the chromosomal instability of PARP-1(-/)- primary cells can be explained by the repair defect associated to PARP-1 deficiency. Finally, no interaction between PARP-1 and the telomerase reverse transcriptase subunit, Tert, was found using the two-hybrid assay.
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TL;DR: In this paper , a label-free electrochemical impedance detection method based on the large amount of phosphate groups (PO43-) on the surface of PAR was proposed, and the calculated detection limit was 0.003 U.
1 citations
01 Jan 2002
TL;DR: This dissertation focuses on the investigation of combination therapy in the treatment of cancer with special emphasis on targeting telomere and telomerase, and recently demonstrated that paclitaxel treatment resulted in shortening and deletion o f telomeres, and a transient increase in telomersase activity which occurred after telomer damage.
Abstract: Cancer is the second leading cause of death in the United States exceeded only by heart disease. The standard treatment regimens include surgery, radiation, chemotherapy, or a combination of the latter. The work presented in this dissertation focuses on the investigation of combination therapy in the treatment o f cancer with special emphasis on targeting telomere and telomerase. Telomeres consist o f a tandem array of G-rich sequences that serve to protect the structural integrity o f the eukaryotic chromosome. In normal somatic cells telomeres shorten with each cellular division until crisis, whereas 80-90% o f cancer cells are able to compensate for the telomere loss with the enzyme telomerase. Paclitaxel is one of the most important anticancer drugs developed in the last two decades, and has shown significant activity against various human solid tumors, i.e., ovarian, head and neck, bladder, breast, and lung cancers. Paclitaxel enhances tubulin polymerization, promotes microtubule assembly, and stabilizes microtubule dynamics, resulting in inhibition of cell proliferation and apoptosis. We recently demonstrated that paclitaxel treatment resulted in shortening and deletion o f telomere, and a transient increase in telomerase activity which occurred after telomere damage. Based on these events we postulate that the upregulation of telomerase
1 citations
Cites background from "Normal telomere length and chromoso..."
...or Ku80‘* mice have a significant increase in end-to-end fused chromosomes at the telomere, indicating that their function is important for the protection of the chromosome by means o f a telomeric association (64, 67, 68)....
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01 Jan 2004
TL;DR: A Model for Telomere Rapid Deletion (TRD) in S. cerevisiae and humans and growth arrest, senescence, and TIF induction by TRF2AB 108 Figure 3-4.
Abstract: List of F i g u r e s Figure 1-1. Cellular senescence inhuman somatic cells 6 Figure 1-2. Telomerase in S. cerevisiae and humans 9 Figure 1-3. Schematic of human T T A G G G repeat binding factors, TRF1 and TRF2.... 20 Figure 1-4. Telomere structure and proteins in mammals 27 Figure 2-1. Schematic and alignment of hTel2 49 Figure 2-2. Expression of hTel2 assessed by Western and IF 52 Figure 2-3. Endogenous hTel2 does not associate with telomeres 55 Figure 2-4. Tel2 does not interact with telomeric proteins by IP 57 Figure 2-5. hTel2 foci do not colocalize with P C N A foci, centromeres, or IRIFs 59 Figure 2-6. hTel2 foci co-localizes with P M L nuclear bodies 61 Figure 2-7. hTel2 localization in meiotic spermatocytes 63 Figure 2-8. hTel2 localizes to centrosomes in mouse and human cells 65 Figure 2-9. Effect of Myc_Tel2 alleles on TRF length in HTC75 and IMR90 cells 68 Figure 2-10. Effect of FLAG_Tel2 on TRF length in BJ/hTERT and HeLal.2.11 69 Figure 2-11. Effect of Tel2 on TRF length in HTC75 and SK-HEP-1 cells 72 Figure 2-12. Effect of Tel2 on TRF length in HTC75 and SK-HEP-1 cells 73 Figure 2-13. Depletion of Tel2 by siRNA results in cell death 76 Figure 2-14. Depletion of Tel2 by siRNA results in the accumulation of abnormal early metaphases 78 Figure 2-15. Depletion of Tel2 by siRNA results in the accumulation of abnormal early metaphases 80 Figure 2-16. Tel2 depletion causes defects in chromosome condensation 82 Figure 2-17. hTel2 expression rescues Tel2 depletion mediated defects in chromosome condensation 83 Figure 2-18. Overexpresion of Tel2 impairs the accumulation of cells in G 2 after IR. ...85 Figure 3-1. A Model for Telomere Rapid Deletion (TRD) in S. cerevisiae 99 Figure 3-2. ChIP of telomeric proteins in cells expressing TRF2AB 106 Figure 3-3. Growth arrest, senescence, and TIF induction by TRF2AB 108 Figure 3-4. TRF2AB results in the loss of duplex telomeric D N A in human and mouse cells 110 Figure 3-5. Quantitation of telomere blots after TRF2AB expression 112 Figure 3-6. TRF2AB induces increased single-stranded D N A at telomeres 114 Figure 3-7. TRF2AB induces stochastic telomere loss telomere associations 117
1 citations
Cites background from "Normal telomere length and chromoso..."
...[147, 151] although the latter defect is a matter of some debate [152, 153]....
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01 Jan 2018
Cites background from "Normal telomere length and chromoso..."
...After several rounds of division, telomeres eventually reach a critically short length, which activates the pathways for senescence and cell death (59,60) A progressive decline in telomere length may also occur due to DNA damage....
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01 Jul 2002
TL;DR: It is reported that the combined expression of adenovirus E1A, Ha-RasV12, and MDM2 is sufficient to convert a normal human cell into a cancer cell, and transformation did not require telomerase activation.
Abstract: : Our knowledge of the transformation process has emerged largely from studies of primary rodent cells and animal models. However, numerous attempts to transform human cells using oncogene combinations that are effective in rodents have proven unsuccessful. These findings strongly argue for the study of homologous experimental systems. Here we report that the combined expression of adenovirus E1A, Ha-RasV12, and MDM2 is sufficient to convert a normal human cell into a cancer cell. Notably, transformation did not require telomerase activation. Therefore, activation of telomere maintenance strategies is not an obligate characteristic of tumorigenic human cells. Activation of telomerase, and consequently telomere maintenance, is a common characteristic of human tumors. Existing models of human cancer cells, created by the introduction of defined genetic alterations, all include telomerase activation as an obligate component of the transformed phenotype. Here we demonstrate that normal human cells can be converted into cancer cells, capable of forming tumors in immunocompromised mice in the absence of telomerase activation or an alternative telomere maintenance strategy. This suggests that alterations in telomere biology must be viewed similarly to genomic instability as catalysts of transformation rather than as central components of the transformed phenotype.
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TL;DR: P16 seems to act in a regulatory feedback circuit with CDK4, D-type cyclins and retinoblastoma protein, and inhibits the catalytic activity of theCDK4/cyclin D enzymes.
Abstract: The division cycle of eukaryotic cells is regulated by a family of protein kinases known as the cyclin-dependent kinases (CDKs). The sequential activation of individual members of this family and their consequent phosphorylation of critical substrates promotes orderly progression through the cell cycle. The complexes formed by CDK4 and the D-type cyclins have been strongly implicated in the control of cell proliferation during the G1 phase. CDK4 exists, in part, as a multi-protein complex with a D-type cyclin, proliferating cell nuclear antigen and a protein, p21 (refs 7-9). CDK4 associates separately with a protein of M(r) 16K, particularly in cells lacking a functional retinoblastoma protein. Here we report the isolation of a human p16 complementary DNA and demonstrate that p16 binds to CDK4 and inhibits the catalytic activity of the CDK4/cyclin D enzymes. p16 seems to act in a regulatory feedback circuit with CDK4, D-type cyclins and retinoblastoma protein.
3,716 citations
"Normal telomere length and chromoso..." refers methods in this paper
...As control for the two-hybrid assay we show interaction between the cell cycle proteins CDK4 and p16 as described previously (Table VI; Serrano et al., 1993)....
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TL;DR: The DNA of telomeres—the terminal DNA-protein complexes of chromosomes—differs notably from other DNA sequences in both structure and function, and has been shown to be essential for telomere maintenance and long-term viability.
Abstract: The DNA of telomeres--the terminal DNA-protein complexes of chromosomes--differs notably from other DNA sequences in both structure and function. Recent work has highlighted its remarkable mode of synthesis by the ribonucleoprotein reverse transcriptase, telomerase, as well as its ability to form unusual structures in vitro. Moreover, telomere synthesis by telomerase has been shown to be essential for telomere maintenance and long-term viability.
3,139 citations
TL;DR: Electron microscopy reported here demonstrated that TRF2 can remodel linear telomeric DNA into large duplex loops (t loops) in vitro, which may provide a general mechanism for the protection and replication of telomeres.
2,413 citations
TL;DR: Results indicate that telomerase is essential for telomere length maintenance but is not required for establishment of cell lines, oncogenic transformation, or tumor formation in mice.
2,066 citations
"Normal telomere length and chromoso..." refers background or methods in this paper
...These Robertsonian fusions are different from those found in late generation telomerase-deficient mice that have critically short telomeres (Blasco et al., 1997)....
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...5 embryos derived from heterozygous crosses as described (Blasco et al., 1997)....
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...Telomeres have an essential role in chromosome stability and are proposed to be biological determinants in the processes of tumorigenesis and aging (for reviews see Blackburn, 1991; Autexier and Greider, 1996; Greider, 1996; Blasco et al., 1997; Lee et al., 1998)....
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...Then the plugs were digested with MboI overnight and run in a pulse field gel electrophoresis as described (Blasco et al., 1997)....
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TL;DR: The history and present situation of Spanish language, culture, literature, cuisine, tourism, and more are explored in more detail in this booklet.
Abstract: TELOMERES DEFINED . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 579 TELOMERE FUNCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 580 SEQUENCE AND STRUCTURE OF TELOMERES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 581 SOLUTIONS FOR REPLICATION OF DNA TERMINI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 586 STRUCTURE OF SUBTELOMERIC REGIONS.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 589 FORMA TION OF TELOMERES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ... . . . . . .. 591 PROTEINS THAT INTERACT WITH TELOMERES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 594 ARE TELOMERES REALLY ESSENTIAL? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 597 FUTURE PROSPECTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 598
1,923 citations
"Normal telomere length and chromoso..." refers background in this paper
...Vertebrate telomeres consist of tandem repeats of the sequence TTAGGG (for review see Blackburn, 1991)....
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...Telomeres have an essential role in chromosome stability and are proposed to be biological determinants in the processes of tumorigenesis and aging (for reviews see Blackburn, 1991; Autexier and Greider, 1996; Greider, 1996; Blasco et al., 1997; Lee et al., 1998)....
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