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 demonstrate here that stilbene estrogen (diethylstilbestrol) is converted to nuclear protein binding metabolite(s) both in vitro and in vivo. In vitro reaction of DES with nuclei from hamster liver or kidney in the presence of cumene hydroperoxide or NADPH revealed binding of [3H]DES in nuclear proteins (histones; nonhistones precipitable by 2% TCA, NH2; nonhistones soluble in 2% TCA, NH30). The binding was significantly inhibited by cytochromes P450 inhibitors. In an in vitro system [3H]DES quinone, one of the metabolites of DES, was able to bind to pure nonhistone proteins RNA polymerase and DNA polymerase. The binding of [3H]DES quinone to nonhistones RNA polymerase and DNA polymerase was inhibited by low molecular weight thiols, i.e. glutathione and cysteine, or thiol modifiers, such as n-ethylmaleimide, dithionitrobenzoic acid and hydroxymercuric benzoate. DES and DES metabolites inhibited transcriptional activity. In vivo [3H]DES was able to bind to nuclear proteins of hamster liver, kidneys and testes. The level of in vivo [3H]DES binding to all three types of nuclear proteins (histones, NH2, NH30) in the kidney (target organ) was two or more fold higher than that observed in the liver or testis (nontarget organs). Four nuclear NH30 proteins (mol wts.: 56, 37, 33 and 28 kDa) were irreversibly bound to [3H]DES in vivo. The in vivo binding of [3H]DES to transcriptionally active chromatin NH30 proteins also was observed. The data reported here establish that DES was able to bind to liver or kidney nuclear proteins in vitro, which was catalyzed by nuclear enzymes when fortified with an appropriate cofactor. DES quinone may be one of the protein binding metabolites. DES and DES metabolites inhibited transcriptional activity. The level of in vivo binding of [3H] DES to nuclear proteins of kidney (target organ) was double in comparison with that observed in liver or testis (nontarget organs). In vivo modifications in the chromatin proteins may be a factor in the development of DES-induced renal carcinogenesis is not clear.
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PMID:In vivo binding of diethylstilbestrol to nuclear proteins of kidneys of Syrian hamsters. 773 58

We report here the alteration(s) in the expression of the DNA repair gene, DNA polymerase beta, in kidney tumors induced by stilbene estrogen (diethylstilbestrol, DES). RT-PCR, slot blotting, and Northern blotting experiments revealed that expression of DNA polymerase beta (DNA pol beta) was several fold lower in stilbene-estrogen-induced kidney tumors than in age-matched controls. Several mutations were identified in DNA pol beta mRNA from DES-induced kidney tumors, but not in age-matched control kidney. The mutations in DNA pol beta mainly occurred in the catalytic domain of pol beta, and not in the DNA binding domain. All the mutations produced a stop codon at nucleotide 199 indicating that a protein of aberrant size may be synthesized. These data suggest that mutation of DNA pol beta coupled with attenuation in expression might compromise the DNA repair system. This in turn may allow a greater error rate during DNA repair and the accumulation of lesions in the genome.
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PMID:Mutations in DNA polymerase beta mRNA of stilbene estrogen-induced kidney tumors in Syrian hamster. 865 81

We have demonstrated previously that diethylstilbestrol is metabolized to diethylstilbestrol reactive metabolites by mitochondrial enzymes in vitro. In vitro, these reactive intermediates bind to mitochondrial DNA. Here we have investigated the in vivo formation of diethylstilbestrol adducts with mitochondrial DNA, the nature of mitochondrial DNA-diethylstilbestrol adducts, and the influence of diethylstilbestrol adduction on in vitro replication of a mitochondrial gene. Diethylstilbestrol administration to male hamsters produced several adducts in mitochondrial DNA of both kidney and liver. The total relative adduct levels were 5- to 6-fold higher in mitochondrial DNA than in nuclear DNA. The chromatographic mobility of mitochondrial DNA adducts formed in vivo were similar to that of dGMP-DES quinone adducts formed in vitro. The identity of mitochondrial DNA adducts formed in vivo was further confirmed as dGMP-diethylstilbestrol quinone adducts by rechromatography and cochromatography. Using a DNA polymerase arrest assay we found that the DES quinone attack on a mitochondrial respiratory gene, i.e., the gene for subunit III of cytochrome c oxidase (COIII), was specific for guanine residues that were adjacent to cytosine residues. Long-term treatment with diethylstilbestrol produced tumors in the kidney, and the level of COIII transcripts was 5- to 10-fold higher in tumor samples than age-matched control kidneys. These findings suggest that i) mitochondrial DNA appears more susceptible to formation of diethylstilbestrol adducts than nuclear DNA, ii) the DNA adducts formed by DES were predominantly with guanines, iii) the adducted bases stopped DNA polymerase-mediated in vitro replication of the COIII gene, and iv) long-term exposure of hamsters to diethylstilbestrol elevated the expression of COIII mRNA. These results suggest that obstruction of replication of the mitochondrial genes by covalent modifications of the mitochondrial DNA by diethylstilbestrol may produce mitochondrial genomic instability in vivo and may provide an explanation for the DES-induced mitochondrial structural abnormality.
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PMID:Base sequence-specific attack of stilbene estrogen metabolite(s) on the mitochondrial DNA: implications in the induction of instability in the mitochondrial genome in the kidney of Syrian hamsters. 1125 79