Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:6.5.1.2 (DNA ligase)
 2,749 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Knowledge of inherited and sporadic mutations in known and candidate cancer genes may influence clinical decisions. We have developed a mutation scanning method that combines thermostable EndonucleaseV (Endo V) and DNA ligase. Variant and wild-type PCR amplicons are generated using fluorescently labeled primers, and heteroduplexed. Thermotoga maritima (Tma) EndoV recognizes and primarily cleaves heteroduplex DNA one base 3' to the mismatch, as well as nicking matched DNA at low levels. Thermus species (Tsp.) AK16D DNA ligase reseals the background nicks to create a highly sensitive and specific assay. The fragment mobility on a DNA sequencing gel reveals the approximate position of the mutation. This method identified 31/35 and 8/8 unique point mutations and insertions/deletions, respectively, in the p53, VHL, K-ras, APC, BRCA1, and BRCA2 genes. The method has the sensitivity to detect K-ras mutations diluted 1 : 20 with wild-type DNA, a p53 mutation in a 1.7 kb amplicon, and unknown p53 mutations in pooled DNA samples. EndoV/Ligase mutation scanning combined with PCR/LDR/Universal array proved superior to automated DNA sequencing for detecting p53 mutations in colon tumors. This technique is well suited for scanning low-frequency mutations in pooled samples and for analysing tumor DNA containing a minority of the unknown mutation.
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PMID:An endonuclease/ligase based mutation scanning method especially suited for analysis of neoplastic tissue. 1189 24

Inhibition of mTOR by rapamycin is an important approach in cancer therapy. In early clinical trials, tuberous sclerosis complex (TSC)-related kidney tumours were found to regress following rapamycin treatment. Since loss of function of the DNA repair OGG1 enzyme has a major role in multistep carcinogenesis of the kidney and other organs, we investigated the effect of rapamycin on OGG1 regulation. Treatment of HK2 cells, mouse Tsc-deficient cells and human VHL-deficient cells (786-O) with rapamycin resulted in decrease in p70S6K phosphorylation at Thr(389), and increase in the expression of NF-YA and OGG1 proteins. In addition, rapamycin increased OGG1 promoter activity in cells transfected with OGG1 promoter construct. Furthermore, rapamycin increased the phosphorylation at Thr(172) of the energy sensor AMPK. Downregulation of AMPK phosphorylation by high glucose (HG) increases the phosphorylation of p70S6K and decreases the protein expression of NF-YA and OGG1. Pretreatment of the cells with rapamycin before exposure to HG reversed the effects of HG. However, downregulation of AMPK by dominant negative (DN)-AMPK in Tsc2(+/-) cells abolished AMPK and decreased OGG1 expression. In contrast, transfection of Tsc2(+/-) cells with DN-S6K abolished p70S6K phosphorylation and increased OGG1 expression, a response enhanced by rapamycin. Treatment of Tsc2(+/-) mice with rapamycin resulted in activation of AMPK, downregulation of phospho-p70S6K and enhanced OGG1 expression. Our data show that inhibition of mTOR can activate AMPK and lead to upregulation of DNA repair enzyme OGG1. These data comprise the first report to provide one mechanism whereby rapamycin might prevent or inhibit the formation and progression of certain cancers.
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PMID:Novel mechanism of reducing tumourigenesis: upregulation of the DNA repair enzyme OGG1 by rapamycin-mediated AMPK activation and mTOR inhibition. 2065 72