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)

The tuberous sclerosis complex (TSC) is caused by defects in one of two tumor suppressor genes, TSC-1 or TSC-2. The TSC-2 gene encodes tuberin, a protein involved in the pathogenesis of kidney tumors, both angiomyolipomas and renal cell carcinomas. We investigated a potential role for tuberin in regulating a key DNA repair pathway. Downregulation of tuberin in human renal epithelial cells using siRNA resulted in a marked decrease in the abundance of the 8-oxoG-DNA glycosylase (OGG1). Mouse embryonic fibroblasts deficient in tuberin (TSC2(-/-) and TSC2(+/-)) also had markedly decreased OGG1 mRNA and protein expression, as well as undetectable OGG1 activity accompanied by accumulation of 8-oxodG. Gel shift analyses and chromatin immunoprecipatation identified the transcription factor NF-YA as a regulator of OGG1 activity. The binding of NF-YA to the OGG1 promoter was significantly reduced in TSC2(-/-) compared with TSC2(+/+) cells. Introduction of TSC2 cDNA into the tuberin-deficient cells restored NF-YA and OGG1 expression. Transcriptional activity of the OGG1 promoter was also decreased in tuberin-null cells. In addition, mutation of both CAAT boxes, the sites to which NF-YA binds, completely inhibits OGG1 promoter activity. These data provide the first evidence that tuberin regulates a specific DNA repair enzyme, OGG1. This regulation may be important in the pathogenesis of kidney tumors in patients with TSC.
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PMID:Tuberin regulates the DNA repair enzyme OGG1. 1798 14

The tuberous sclerosis complex (TSC) is caused by defects in one of two tumor suppressor genes, TSC-1 or TSC-2. TSC-2 gene encodes tuberin, a protein involved in the pathogenesis of kidney tumors, both angiomyolipomas and renal cell carcinomas. On the other hand, mice-deficient in the DNA repair enzyme OGG1 spontaneously develop adenoma and carcinoma. Downregulation of tuberin results in a marked decrease of OGG1 and accumulation of oxidative DNA damage, (8-oxodG) in cultured cells. In addition, tuberin haploinsufficiency is associated with the loss of OGG1 and accumulation of 8-oxodG in rat kidney tumor. Deficiency in tuberin results in decreased OGG1 and NF-YA protein expression and increased 8-oxodG in kidney tumor from TSC patients. In the current study, molecular mechanisms by which tuberin regulates OGG1 were explored. The deficiency of tuberin was associated with a significant decrease in NF-YA and loss of OGG1 in kidney tumors of Eker rat. Downregulation of tuberin by siRNA resulted in a marked decrease in NF-YA and OGG1 protein expression in human renal epithelial cells. Localization of NF-YA in wild type and tuberin-deficient cells was examined by western blot and immunostaining assays. In wild type cells, NF-YA was detected in the nucleus while in tuberin deficient cells in the cyotoplasm. Introducing adenovirus-expressing tuberin (Ad-TSC2) into tuberin-deficient cells restored the nuclear localization of NF-YA. These data define a novel mechanism of regulation of OGG1 through tuberin. This mechanism may be important in the pathogenesis of kidney tumors in patients with TSC disease.
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PMID:Molecular mechanism of regulation of OGG1: tuberin deficiency results in cytoplasmic redistribution of transcriptional factor NF-YA. 2004 97

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