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

We investigated the effects of fission yeast replication genes on telomere length maintenance and identified 20 mutant alleles that confer lengthening or shortening of telomeres. The telomere elongation was telomerase dependent in the replication mutants analyzed. Furthermore, the telomerase catalytic subunit, Trt1, and the principal initiation and lagging-strand synthesis DNA polymerase, Polalpha, were reciprocally coimmunoprecipitated, indicating these proteins physically coexist as a complex in vivo. In a polalpha mutant that exhibited abnormal telomere lengthening and slightly reduced telomere position effect, the cellular level of the Trt1 protein was significantly lower and the coimmunoprecipitation of Trt1 and Polalpha was severely compromised compared to those in the wild-type polalpha cells. Interestingly, ectopic expression of wild-type polalpha in this polalpha mutant restored the cellular Trt1 protein to the wild-type level and shortened the telomeres to near-wild-type length. These results suggest that there is a close physical relationship between the replication and telomerase complexes. Thus, mutation of a component of the replication complex can affect the telomeric complex in maintaining both telomere length equilibrium and telomerase protein stability.
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PMID:Replication proteins influence the maintenance of telomere length and telomerase protein stability. 1269 6

Telomerase is a ribonucleoprotein DNA polymerase that has been associated with cell proliferation, cell survival and apoptosis inhibition. Telomerase is regulated by specific growth factors, cytokines and hormones. The present study examines the effect of GH on telomerase activity and identifies the signal transduction pathway involved in this process in Chinese hamster ovary (CHO)4 cells, which express rat GH receptor cDNA. Telomeric repeat amplification protocol assays demonstrated that treating CHO4 cells with increasingly high doses of GH up-regulated telomerase activity with the maximum activation at 24 h. Similarly, GH activated telomerase in another cell system, primary cultures of rat hepatocytes. The telomerase activation in CHO4 cells was produced with an increase in hamster telomerase catalytic subunit (hamTERT) mRNA expression. The telomerase activity induced by GH was specifically blocked by the phosphatidylinositol 3'-kinase (PI3-K) inhibitor, LY294002, but not by the MAP kinase kinase inhibitor, PD98059. These findings suggest that GH could activate telomerase through the direct activation of TERT transcription, as well as through the PI3-K signalling pathway.
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PMID:Direct activation of telomerase by GH via phosphatidylinositol 3'-kinase. 1593 Jan 68

Telomerase is a specialized DNA polymerase that extends the 3' ends of eukaryotic linear chromosomes, a process required for genomic stability and cell viability. Here we present the crystal structure of the active Tribolium castaneum telomerase catalytic subunit, TERT, bound to an RNA-DNA hairpin designed to resemble the putative RNA-templating region and telomeric DNA. The RNA-DNA hybrid adopts a helical structure, docked in the interior cavity of the TERT ring. Contacts between the RNA template and motifs 2 and B' position the solvent-accessible RNA bases close to the enzyme active site for nucleotide binding and selectivity. Nucleic acid binding induces rigid TERT conformational changes to form a tight catalytic complex. Overall, TERT-RNA template and TERT-telomeric DNA associations are remarkably similar to those observed for retroviral reverse transcriptases, suggesting common mechanistic aspects of DNA replication between the two families of enzymes.
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PMID:Structural basis for telomerase catalytic subunit TERT binding to RNA template and telomeric DNA. 2035 74

The mechanisms of action of gemcitabine (GEM) and paclitaxel (PTX) have been well investigated, and shown to be the inhibition of DNA polymerase and polymerization of tubulin, respectively. Meanwhile, genomic research has revealed that mutations in the K-RAS oncogene occur in over 90% of pancreatic cancer. Oncogenic alteration rewires alternative metabolic pathways to satisfy the demands of growth. The K-RAS oncogene also has been shown to upregulate glycolysis and glutaminolysis. However, it is still unclear whether K-RAS independently plays a central role in controlling tumor metabolism. Here, we conducted a metabolomic analysis of a simple oncogenic K-RAS cell line model constructed using human telomerase catalytic subunit-immortalized human pancreatic epithelial nestin-expressing cell lines with and without K-RASG12D. We also investigated the effect of GEM and PTX on these cells. As a result, it was shown in the cell with K-RASG12D that the level of lactate was increased and glutamic acid, glutamine, and aspartic acid levels were decreased. In the nucleotide metabolism, GEM-treated cells showed metabolic changes, whereas these phenomena were not observed in PTX-treated cells. In conclusion, it was suggested that K-RASG12D independently modified tumor metabolism and the difference between GEM and PTX in the nucleotide metabolism was revealed.
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PMID:Metabolic profiling of gemcitabine- and paclitaxel-treated immortalized human pancreatic cell lines with K-RASG12D. 2823 30