Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.7.7 (DNA polymerase)
 17,007 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Telomerase is a telomere-specific DNA polymerase consisting of protein and RNA components, which is activated in germline cells and the majority of cancers and serves to counter the consequences of telomere shortening. The protein component, hTERT, is believed to be the catalytic subunit of human telomerase and its expression at the mRNA level correlates well with telomerase activity in vitro. Current techniques for assaying telomerase activity detect only the mean activity in a sample and are unable to isolate specific cell sub-populations. This report describes the development and validation of a cellular, immunofluorescence-based flow cytometry assay that allows detection of intranuclear hTERT while maintaining identifiable cell population characteristics. The assay was shown to be both sensitive to changes in telomerase expression and was semi-quantitative. In both cell line differentiation experiments and in primary cells, a good correlation existed between hTERT expression measured by flow cytometry and telomerase activity detected by the telomeric repeat amplification protocol (TRAP). The method developed offers a quick, simple and reproducible cellular-based assay for hTERT expression. This assay will provide a useful, new tool for future investigations, facilitating the analysis of hTERT expression in mixed cell populations.
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PMID:Detection of hTERT protein by flow cytometry. 1118 8

DNA methylation is an epigenetic process involved in embryonic development, differentiation and aging. It is 1 of the mechanisms resulting in gene silencing in carcinogenesis, especially in tumor suppressor genes (e.g., p16, Rb). Telomerase, the DNA polymerase adding TTAGGG repeats to the chromosome end, is involved in the regulation of the replicative life span by maintaining telomere length. This enzyme is activated in germ and stem cells, repressed in normal somatic cells and reactivated in a large majority of tumor cells. The promoter region of the hTERT gene, encoding for the catalytic subunit of human telomerase, has been located in a CpG island and may therefore be regulated at least in part by DNA methylation. We analyzed the methylation status of 27 CpG sites within the hTERT promoter core region by methylation-sensitive single-strand conformation analysis (MS-SSCA) and direct sequencing using bisulfite-modified DNA in 56 human tumor cell lines, as well as tumor and normal tissues from different organs. A positive correlation was observed among hypermethylation of the hTERT promoter, hTERT mRNA expression and telomerase activity (p < 0.00001). Furthermore, this correlation was confirmed in normal tissues where hypermethylation of the hTERT promoter was found exclusively in hTERT-expressing telomerase-positive samples and was absent in telomerase-negative samples (p < 0.00002). Since tumor tissues contain also nonneoplastic stromal elements, we performed microdissection to allow confirmation that the hTERT promoter methylation truly occurred in tumor cells. Our results suggest that methylation may be involved in the regulation of hTERT gene expression. To our knowledge, this is the first gene in which methylation of its promoter sequence has been found to be positively correlated with gene expression.
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PMID:Hypermethylation of the human telomerase catalytic subunit (hTERT) gene correlates with telomerase activity. 1220 57

The overexpression of DNA polymerase beta (beta-pol) has been identified in lots of human cancers, but the mechanism has seldom been investigated. Telomerase transcriptional element-interacting factor (TEIF) can bind to hTERT promoter, stimulating its transcription and telomerase activities. Here, we report that TEIF could also enhance the expression of beta-pol at transcription level. TEIF could specifically activate transcription of beta-pol promoter, but not that of DNA polymerase alpha or delta promoter. The responsible sequences for binding of TEIF were revealed as GC-rich elements dispersing from +19 to -29 nt of beta-pol promoter, which due to mutations caused decreasing in binding of TEIF and apparent losing of transactivation activity. The in vivo interaction between TEIF and beta-pol promoter was identified by chromatin immunoprecipitation assay. Besides, ectopic expression of TEIF in HeLa cells could upregulate both levels of endogenous beta-pol mRNA and protein, and consequently increases resistance to the oxidative stress of H2O2. The data may provide new clue to the elucidation of beta-pol overexpression in cancers and also a functional link between beta-pol and telomerase.
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PMID:Transcriptional upregulation of DNA polymerase beta by TEIF. 1596 46

One of the core regulators of cellular aging are telomeres, repetitive DNA sequences at the ends of chromosomes that are maintained by the ribonucleoprotein DNA polymerase complex, telomerase. Recently, we demonstrated that knockdown of the 37kDa/ 67kDa laminin receptor (LRP/LR), a protein that promotes cell viability in tumorigenic and normal cells, reduces telomerase activity. We therefore hypothesized that upregulating LRP/LR might increase telomerase activity and impede aging. Here we show that overexpression of LRP::FLAG resulted in significantly elevated hTERT levels, telomerase activity and telomere length, respectively, with concomitantly reduced levels of senescence markers. These data suggest a novel function of LRP/LR hampering the onset of senescence through elevating hTERT levels and telomerase activity, respectively. LRP::FLAG might therefore act as a potential novel anti-aging drug through the impediment of the cellular aging process.
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PMID:37 kDa LRP::FLAG enhances telomerase activity and reduces senescent markers in vitro. 2915 24