• Proceedings of the Korean Society of Developmental Biology Conference
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• 2003.10a
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• pp.111-111
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• 2003

Telomeres are the end of chromosomes and consist of a tandem repeat sequence of (TTAGGG)n and associated proteins. Telomerase is a ribonucleoprotein which act as a template for the synthesis of telomeric DNA. Telomeres are essential for chromosome stability and are related with cell senescence, apoptosis and cancer. Even though telomeres and telomerase have been studied extensively, very little is known about telomere dynamics in embryonic cells. This study was carried out to analyze the telomeres distribution and telomerase activity of chicken cells during embryonic and developmental stages. The target cells for analysing were sperms, ovulated ova, early embryonic cells and the cells from brain, heart, liver, kidney and germinal tissue in fetus. Telomeres distribution on target cells was analyzed by Q-FISH (Quantitation-Fluorescence in situ Hybridization) techniques using a chicken telomere repeat probe. Telomerase activity was performed by TRAP assay (Telomeric repeat Amplification Protocol) with target DNA. In results, the telomeres of chicken were found at the ends of all chromosomes. In addition, chicken had interstitial telomeres on chromosomes 1, 2 and 3. Telomerase activity was highly detectable in early embryonic cells, germinal tissues and kidney cells. Whereas telomerase activity was gradually down-regulated when the organs, including brain, heart, and liver, were developed from embryos. In the distribution of telomeric DNA on the embryonic and developmental stages, most of the cells was gradually decreased in telomere quantity during ontogenesis.

• Biomedical Science Letters
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• v.12 no.4
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• pp.399-403
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• 2006

Cervical cancer is one of the most prevalent cancers developed in women worldwide, and human papillomavirus (HPV) type 16 is the most common agent linked to human cerivical carcinoma. Viral oncogenes E6 and E7 are selectively ratined and expressed in carcinoma cells infected with human papillomavirus type 16 and cooperated with each other in immortalization and transformation of primary keratinocytes. Because of HPV oncogenesis mechanism was not completely solved, the more studies be required thoroughly. In the present study, to investigate the telomere independent role of telomerase in HPV oncogenesis, we constructed the E6 mutant, E7, E6/E7 and hTERT over-expressed stable cells with a telomerase negative cell line, SW13. Expressions of Inserted genes were measured by RT-PCR. E6, E7 and hTERT genes were well expressed in each cell lines comparing with the control groups. By analyzing the cell morphology under the microscope, hTERT clone size was a more smaller than the mock control but oncogene expressed clones were slightly lengthened the marginal region. In addition, hTERT cells has also, a tendency of brief dividing time compared to the mock control. To determine whether telomerase activity associated with a HPV oncogenesis by oncoprotein expression, we performed the PCR based TRAP assay and Northern blot analysis. In TRAP assay data, telomerase activities in hTERT and oncogene clones were more increased than the mock control. In addition, SW13/ E6/E7 cells appeared a extremely increased activity than any other clones. Induced TERT mRNA by E6/E7 wasn't, however, detected in Northern blotting. In conclusion, these findings suggest that telomerase activity closely associated the HPV oncogenesis and E6/E7 co-expression is a most important factor of telomerase activity.

• Clinical and Experimental Reproductive Medicine
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• v.36 no.2
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• pp.101-109
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• 2009

Objective: This study was carried out to analyze the amount of telomeric DNA and telomerase activity in early bovine embryos. Methods: The amount of telomeric DNA in early bovine embryos at the 8 cell, morula and blastocyst stages was analyzed by Quantitative Fluorescence In Situ Hybridization (Q-FISH) technique using a bovine telomeric DNA probe. Telomerase activity was analyzed by Telomeric Repeat Amplification Protocol (TRAP assay). Results: The relative amount of telomeric DNA in early bovine embryos was gradually increased from 8 cell to blastocyst stage. It was not significantly associated with the grade of embryo quality. While telomerase activity was detected in the early bovine embryos at these stages, it significantly increased at morula stage and showed maximum activity at the blastocyst stage. Conclusion: The amount of telomeric DNA and the telomerase activity of bovine embryos increase during the progression of early embryogenesis, suggesting a positive correlation between telomeric DNA and telomerase activity. The telomerase activity seems to increase to maintain the levels of telomeric DNA through embryo development which are required for extensive cell division.

• Journal of Chest Surgery
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• v.30 no.7
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• pp.701-707
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• 1997

Although many reseraches have been persued to detect the molecular tumor marker to define the cancer, ideal tumor marker which speak for the characteristics of malignancy and has high sensitivity and specificity is not known. One of the characteristics of the malignant cells is indefinite proliferative potential, in other word, immortality. The expression of telomerase and stabilization of te10meres are con omitant with the attaiunent of immortality in tumor cells; thus the measurement of telomerase activity in clinically obtained tumor samples may provide important information which would be useful as a diagnostic marker to detect immortal cancer cells. Telomerase activity was analyzed in 12 non-small cell . lung cancer cell lines and 41 primary non-small cell lung cancers with the use of a PCR-based assay. All the cell lines and the majority of tumors displayed telomerase activity, but telomerase was not detectable in most of the corresponding pathologically-normal tissues. Telomere length was not correlated with telomerase activity. The present study indicate that measurement of telomerase activity may be useful as a molecular tumor marker in non-small cell lung cancer.

• Journal of Animal Reproduction and Biotechnology
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• v.34 no.2
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• pp.93-99
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• 2019

Telomeres are known as a specialized region in the end of chromosomes to protect DNA destruction, but their lengths are shortened by repetition of cell division. This telomere shortening can be preserved or be elongated by telomerase and TERT expression. Although a certain condition in the cells may affect to the cellular and molecular characteristics, the effect of differentiation induction to telomere length and telomerase activity in mesenchymal stem cells (MSCs) has been less studied. Therefore, the present study aimed to uncover periodical alterations of telomere length, telomerase activity and TERT expression in the dental pulp-derived MSCs (DP-MSCs) under condition of differentiation inductions into adipocytes and osteoblasts on a weekly basis up to 3 weeks. Shortening of telomere was significantly (p < 0.05) identified from early-middle stages of both differentiations in comparison with undifferentiated DP-MSCs by non-radioactive chemiluminescent assay and qRT-PCR method. Telomere length in undifferentiated DP-MSCs was 10.5 kb, but the late stage of differentiated DP-MSCs which can be regarded as the adult somatic cell exhibited 8.1-8.6 kb. Furthermore, the relative-quantitative telomerase repeat amplification protocol or western blotting presented significant (p < 0.05) decrease of telomerase activity since early stages of differentiations or TERT expression from middle stages of differentiations than undifferentiated state, respectively. Based on these results, it is supposed that shortened telomere length in differentiated DP-MSCs was remained along with prolonged differentiation durations, possibly due to weakened telomerase activity and TERT expression. We expect that the present study contributes on understanding differentiation mechanism of MSCs, and provides standardizing therapeutic strategies in clinical application of MSCs in the animal biotechnology.

• Asian Pacific Journal of Cancer Prevention
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• v.13 no.5
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• pp.2305-2309
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• 2012

Crocin, the main pigment of Crocus sativus L., has been shown to have antiproliferative effects on cancer cells, but the involved mechanisms are only poor understood. This study focused on probable effect of crocin on the immortality of hepatic cancer cells. Cytotoxicity of crocin ($IC_{50}$ 3 mg/ml) in hepatocarcinoma HepG2 cells was determined after 48 h by neutral red uptake assay and MTT test. Immortality was investigated through quantification of relative telomerase activity with a quantitative real-time PCR-based telomerase repeat amplification protocol (qTRAP). Telomerase activity in 0.5 ${\mu}g$ protein extract of HepG2 cells treated with 3 mg/ml crocin was reduced to about 51% as compared to untreated control cells. Two mechanisms of inhibition, i.e. interaction of crocin with telomeric quadruplex sequences and down regulation of hTERT expression, were examined using FRET analysis to measure melting temperature of a synthetic telomeric oligonucleotide in the presence of crocin and quantitative real-time RT-PCR, respectively. No significant changes were observed in the $T_m$ telomeric oligonucleotides, while the relative expression level of the catalytic subunit of telomerase (hTERT) gene showed a 60% decrease as compared to untreated control cells. In conclusion, telomerase activity of HepG2 cells decreases after treatment with crocin, which is probably caused by down-regulation of the expression of the catalytic subunit of the enzyme.

• BMB Reports
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• v.31 no.4
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• pp.339-344
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• 1998

The plant flavonoids, including apigenin which is found in especially high concentrations in edible plants, are reported to protect against chronic diseases including several types of cancer. We observed that apigenin inhibited not only the growth of human melanoma cell line SK-MEL 28 but also the telomerase activity. We also noted the telomerase activity inhibition by genistein, a tyrosine kinase inhibitor found in soybean, which suggests that the telomerase activity of SK-MEL 28 cells may be regulated by the protein phosphorylation. Furthermore, we observed that apigenin induced SK-MEL 28 cell apoptosis with p53 upregulation. Taken together, our results indicate that apigenin plays a role as an antimelanoma component in edible plants.

• Asian Pacific Journal of Cancer Prevention
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• v.14 no.11
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• pp.6945-6948
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• 2013

Background: Diosgenin, a steroidal saponin from a therapeutic herb, fenugreek (Trigonellafoenum-graceum L.), has been recognized to have anticancer properties. Telomerase activity is not detected in typical healthy cells, while in cancer cell telomerase expression is reactivated, therefore providing a promising cancer therapeutic target. Materials and Methods: We studied the inhibitory effect of diosgenin on human telomerase reverse transcriptase gene (hTERT) expression which is critical for telomerase activity. MTT- assays and qRT-PCR analysis were conducted to assess cytotoxicity and hTERT gene expression inhibition effects, respectively. Results: MTT results showed that $IC_{50}$ values for 24, 48 and 72h after treatment were 47, 44 and $43{\mu}M$, respectively. Culturing cells with diosgenin treatment caused down-regulation of hTERT expression. Discussion: These results show that diosgenin inhibits telomerase activity by down-regulation of hTERT gene expression in the A549 lung cancer cell line.

• Environmental Analysis Health and Toxicology
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• v.19 no.3
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• pp.235-240
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• 2004

본 연구는 비만세포의 일종인 RBL-2H3 세포주에 대한 hexamethylene bisacetamide (HMBA)의 세포독성 유도 기전이 telomerase의 활성과 관계가 있다는 것에 대한 보고이다. RBL-2H3 세포주에 5mM HMBA를 처리시 그 세포주의 세포성장이 억제 되었다. 기전연구로서 HMBA는 telomerase활성을 억제 하였으며 RT-PCR에 의한 결과 telomerase mRNA발현의 억제에 의한 것이었다. Madl은 telomerase의 발현을 억제하는 억제인자로 잘 알려져 왔으며 이를 확인해본 결과 Madl은 발현은 유의성있게 증가 되었다. 이를 종합해보면, HMBA에 의한 RBL-2H3 세포주에 대한 세포독성은 Madl 발현의 증가에 따른 telomerase발현의 억제에 기인하는 것으로 밝혀졌다.

• Molecules and Cells
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• v.19 no.3
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• pp.303-309
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• 2005

The end of eukaryotic genomic DNA is capped by a specialized structure called as "telomere" which consists of the repetitive array of nucleotide sequence, TTAGGG, in humans and mice, and a variety of binding proteins. Telomerase is a ribonucleoprotein (RNP) complex responsible for the elongation of telomeres to maintain the genomic integrity, and is composed of telomerase reverse transcriptase (TERT), telomerase RNA component (TERC), and their associated factors regulating the catalytic activity of telomerase. Although it is now apparent that telomerase protects cells from apoptosis via the maintenance of genomic integrity by stabilizing telomeres, our understanding for the physiological role of telomerase is yet far from completion, and emerging evidence suggests that telomerase has additional extratelomeric roles in mediating cell survival and anti-apoptotic functions against various cytotoxic stresses. Here we summarize and discuss how telomerase and telomeres are involved in mediating cellular protection against apoptosis.