Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.1.30.1 (S1 nuclease)
 3,660 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In this study, an endogenous factor(s) involved in the suppression of the induction of CYP1A1 was studied. Analyzing the sequences, we found that the sequence of xenobiotic responsive element (XRE) in the upstream region of the human CYP1A1 gene was overlapped with that of the upstream stimulatory factor 1 (USF1)-binding site in mouse metallothionein I promoter. In fact, a gel shift assay using a specific competitor or mutant probes showed that the core sequence of human XRE was specifically recognized by USF1. The amount of USF1 in the nuclear extracts from HepG2 cells was smaller than that from rat and rabbit livers as assayed by the binding to XRE. To determine whether or not USF1 could inhibit the interaction of aryl hydrocarbon receptor (AhR)/AhR nuclear translocator (Arnt) complex with XRE, we transfected USF1-SR alpha expression vector into HepG2 cells. The results showed that no interaction of AhR/Arnt complex with XRE occurred even when the cells were treated with 2,3,7,8-tetrachlorodibenzofuran (TCDF). Furthermore, the S1 nuclease protection assay showed that the induction of CYP1A1 mRNA by 3-methylcholanthrene (MC) was depressed by the transfection of USF1-SR alpha into HepG2 cells. Thus, it is highly possible that USF1 negatively regulates the induction of CYP1A1 in humans.
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PMID:Upstream stimulatory factor 1 (USF1) suppresses induction of CYP1A1 mRNA by 3-methylcholanthrene (MC) in HepG2 cells. 938 70

Unlike most experimental animals, treatment of adult rabbits with 3-methylcholanthrene (MC) does not induce the expression of the CYP1A1 gene. In this study, we show that DNA methylation plays one of the key roles in the suppression of CYP1A1 gene expression. S1 nuclease protection assay showed that the induction of CYP1A1 mRNA by MC occurred in rabbit kidney RK13 cells but not in rabbit lung R9ab cells, while aryl hydrocarbon receptor (AhR) and AhR nuclear translocator (Arnt) mRNAs were expressed in both cells at similar levels. Interestingly, the treatment of R9ab cells with a DNA demethylating agent, 5-aza-2'-deoxycitidine, resulted in the induction of the expression of the CYP1A1 gene by MC. The results indicate that DNA methylation is one of the factors involved in the loss of the MC-induced expression of the CYP1A1 gene. Thus, it seemed that the binding of the AhR/Arnt complex to the xenobiotic-responsive element (XRE) was inhibited by the hypermethylation of CpG dinucleotides within an XRE core sequence (5'-CGTG-3'). To explore this possibility, we compared the methylation status of XRE in R9ab cells with that in RK13 cells. A bisulfite sequence analysis using genomic DNAs from R9ab cells showed that the CpG site within XRE was highly methylated on both coding and non-coding strands. In contrast to this result, the hypomethylation of XRE was seen in RK13 cells. To examine whether or not the binding of the AhR/Arnt heterodimer to XRE is affected by the methylation status of XRE, a gel shift assay using a methylated XRE as a probe was carried out. As expected, the AhR/Arnt complex could not bind to the methylated XRE. From these results, we conclude that the cell type-specific transcription of the rabbit CYP1A1 gene is caused by DNA methylation.
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PMID:Silencing of CYP1A1 expression in rabbits by DNA methylation. 964 36

A systematic survey for the presence of plasmids in 17 different xenobiotic-degrading Sphingomonas strains was performed. In almost all analyzed strains, two to five plasmids with sizes of about 50 to 500 kb were detected by using pulsed-field gel electrophoresis. A comparison of plasmid preparations untreated or treated with S1 nuclease suggested that, in general, Sphingomonas plasmids are circular. Hybridization experiments with labeled gene probes suggested that large plasmids are involved in the degradation of dibenzo-p-dioxin, dibenzofuran, and naphthalenesulfonates in S. wittichii RW1, Sphingomonas sp. HH69, and S. xenophaga BN6, respectively. The plasmids which are responsible for the degradation of naphthalene, biphenyl, and toluene by S. aromaticivorans F199 (pNL1) and of naphthalenesulfonates by S. xenophaga BN6 (pBN6) were site-specifically labeled with a kanamycin resistance cassette. The conjugative transfer of these labeled plasmids was attempted with various bacterial strains as putative recipient strains. Thus, a conjugative transfer of plasmid pBN6 from S. xenophaga BN6 to a cured mutant of strain BN6 and to Sphingomonas sp. SS3 was observed. The conjugation experiments with plasmid pNL1 suggested a broader host range of this plasmid, because it was transferred without any obvious structural changes to S. yanoikuyae B1, Sphingomonas sp. SS3, and S. herbicidovorans. In contrast, major plasmid rearrangements were observed in the transconjugants after the transfer of plasmid pNL1 to Sphingomonas sp. HH69 and of pBN6 to Sphingomonas sp. SS3. No indications for the transfer of a Sphingomonas plasmid to bacteria outside of the Sphingomonadaceae were obtained.
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PMID:Detection and characterization of conjugative degradative plasmids in xenobiotic-degrading Sphingomonas strains. 1517