Dioxin Induces Localized, Graded Changes in Chromatin Structure: Implications for<i>Cyp1A1</i>Gene Transcription

Okino, ST; Whitlock, Jr Jp

doi:10.1128/mcb.15.7.3714

Cited by 78 publications

(61 citation statements)

References 58 publications

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“…Gene Domain Sequence at position number 1 2 3 4 5 6 7 8 9 10 11 more access during transactivation initiated by the DRE-bound activated Ah receptor, a process shown to involve changes in chromatin structure [44]. We note that seven DRE core motifs within the human CYP1A1 gene enhancer including non-functional ones possess counterparts at similar positions in the mouse gene, although the sequence surrounding the core motif partly shows marked differences (Fig.…”

Section: Organismmentioning

confidence: 99%

Functional analysis of the human cytochrome P4501A1 (CYP1A1) gene enhancer

Kress

Reichert

Schwarz

1998

European Journal of Biochemistry

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The environmental contaminant 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD or dioxin) induces gene transcription, a process that requires binding of the activated aryl hydrocarbon receptor (AhR) to dioxinresponsive elements (DREs) within the enhancer region of responsive genes. Most of what is known about the molecular mechanism of AhR-dependent gene activation results from studies on the murine prototype TCDD-responsive gene cytochrome P4501A1 (CYP1A1). Much less is known, however, about the regulation of human TCDD-responsive genes. We have therefore conducted a detailed analysis of the enhancer region of the human CYP1A1 gene. From the ten DRE core motifs investigated within a stretch of 1400 bp in two human tumor cell lines using a ligation-mediated PCR technique, five motifs displayed a TCDD-inducible in vivo footprint. Four of these sites were functional enhancer sequences as demonstrated by a transient expression assay. Based on these data, a distinct functional consensus sequence for DRE motifs within the human CYP1A1 gene is suggested. After introduction of the four functional sites into various mouse hepatoma cell lines, only three exhibited a functional response, suggesting some species differences in CYP1A1 gene regulation. In addition to the footprints at DRE sites, we also detected protein-DNA interactions at three G-rich domains located within the enhancer region of the human CYP1A1 gene. Our data show that, besides some similarities in the regulation of the human and mouse CYP1A1 genes, there also exist some distinct differences, including number, location, and functional consensus sequences of DRE motifs, as well as quantity and location of footprinted G-rich domains.Keywords : CYP1A1; 2,3,7,8-tetrachlorodibenzo-p-dioxin ; Ah receptor; dioxin-responsive elements; gene regulation.2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD or dioxin) is a prototype for a large class of halogenated aromatic hydrocarbons that are widespread and persistent environmental contaminants. In rodents, dioxin produces a broad spectrum of toxic responses and is a potent tumor-promoting agent, while its relevance as a toxicant in humans is less clear (for review see [1]). The diversity of effects are assumed to reflect the ability of TCDD to alter gene expression in a species-specific and tissue-specific manner [2Ϫ4]. Many of the actions of TCDD have been shown to be mediated through an intracellular binding protein, designated the Ah receptor (AhR). This receptor is a member of a distinct class of basic helix-loop-helix (bHLH) transcription factors [5]. The inactive Ah receptor resides in the cytoplasm of target cells in a complex with heat-shock protein Hsp90 and possibly other proteins [6Ϫ9]. Upon binding of a ligand, the receptor is released from Hsp90, and heterodimerizes with a second bHLH protein named Ah-receptor nuclear translocator or ARNT [10]. The resultant AhR/ARNT/ligand complex is able to bind to specific DNA enhancer sequences, termed dioxin-responsive elements (DREs), located in the 5′ regulatory region of respon...

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Section: Organismmentioning

confidence: 99%

Functional analysis of the human cytochrome P4501A1 (CYP1A1) gene enhancer

Kress

Reichert

Schwarz

1998

European Journal of Biochemistry

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“…In vivo footprinting using dimethyl sulfate (DMS; Sigma) was done as described previously (13,14). To analyze DRE 3, we used the following primer set: primer 1, 5 ¶-TTCAATCAAGAGGCGCGAACCT-3 ¶; primer 2, 5 ¶-AACCTCAGCTAGTCGCCCGGGCTCT-3 ¶; and primer 3, 5 ¶-GTCCAGCCCCGCGGCGCCTCTGGCCTT-3 ¶.…”

Section: Methodsmentioning

confidence: 99%

“…In vivo footprinting of AhRC-binding sites. Cells treated with 5-aza-CdR (1 Amol/L) for 7 days and/or TCDD (10 nmol/L) for 2 hours were analyzed by in vivo footprinting as described previously (13,14). N, naked genomic DNA treated with DMS in vitro was also analyzed.…”

Section: Cancer Researchmentioning

confidence: 99%

Epigenetic Inactivation of the Dioxin-Responsive Cytochrome P4501A1 Gene in Human Prostate Cancer

Okino

Pookot

et al. 2006

Cancer Research

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2,3,7, dioxin) is a toxic environmental contaminant that works through dioxin response elements (DRE) to activate gene expression. We tested the hypothesis that cancer-related epigenetic changes suppress dioxin activation of the cytochrome P4501A1 (CYP1A1) gene. 5-Aza-2 ¶-deoxycytidine (5-aza-CdR), an inhibitor of DNA methylation, increases TCDD-inducible CYP1A1 mRNA expression in cancerous LNCaP cells but not in noncancerous PWR-1E and RWPE-1 cells (all human prostate cell lines). Bisulfite DNA sequencing shows that the TCDD-responsive CYP1A1 enhancer is highly methylated in LNCaP cells but not in RWPE-1 cells. In vivo footprinting experiments reveal that unmethylated DRE sites do not bind protein in response to TCDD in LNCaP cells, whereas inducible DRE occupancy occurs in RWPE-1 cells. Pretreatment of LNCaP cells with 5-aza-CdR partially restores TCDD-inducible DRE occupancy, showing that DNA methylation indirectly suppresses DRE occupancy. Chromatin immunoprecipitation experiments reveal that LNCaP cells lack trimethyl histone H3 lysine 4, a mark of active genes, on the CYP1A1 regulatory region, whereas this histone modification is prevalent in PWR-1E and RWPE-1 cells. We also analyzed CYP1A1 enhancer methylation in human prostate tissue DNA. We do not detect CYP1A1 enhancer methylation in 30 DNA samples isolated from noncancerous prostate tissue. In contrast, 11 of 30 prostate tumor DNA samples have detectable CYP1A1 enhancer methylation, indicating that it is hypermethylated in prostate tumors. This is the first report that shows that CYP1A1 is aberrantly hypermethylated in human prostate cancer and has an altered, inaccessible chromatin structure that suppresses its dioxin responsiveness. (Cancer Res 2006; 66(15): 7420-8)

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“…AhRE binding induces chromatin remodelling at the promoter which favours transcription (Elferink & Whitlock 1990, Fujii-Kuriyama et al 1995, Okino & Whitlock 1995. Chromatin structure is also important in maintaining transcriptional silence in the uninduced state (Okino & Whitlock 1995). AHR and ARNT are expressed predominantly in the liver (Dolwick et al 1993, Li et al 1994, and both are essential for cyp1a1 induction (Ryu et al 1996, Foussat et al 1998, Zaher et al 1998, Tomita et al 2000.…”

Section: Cytochrome P-450 Induction Systemmentioning

confidence: 99%

“…4). AhRE binding induces chromatin remodelling at the promoter which favours transcription (Elferink & Whitlock 1990, Fujii-Kuriyama et al 1995, Okino & Whitlock 1995. Chromatin structure is also important in maintaining transcriptional silence in the uninduced state (Okino & Whitlock 1995).…”

Section: Cytochrome P-450 Induction Systemmentioning

confidence: 99%

Conditional transgenic technologies

Ryding

Sharp²,

Mullins³

2001

Journal of Endocrinology

141

103

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Transgenic technology has been revolutionised by the development of techniques that allow temporo-spatial control of gene deletion or expression in transgenic animals. The ability to switch gene expression 'on' or 'off' in restricted tissues at specific times allows unprecedented flexibility for exploring gene function in both health and disease. As use of these techniques grows in all areas of biomedical research, an understanding of this topic is essential. In this review we examine the theory, application and limitations of these strategies, with particular reference to endocrine research.

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Dioxin Induces Localized, Graded Changes in Chromatin Structure: Implications forCyp1A1Gene Transcription

Cited by 78 publications

References 58 publications

Functional analysis of the human cytochrome P4501A1 (CYP1A1) gene enhancer

Functional analysis of the human cytochrome P4501A1 (CYP1A1) gene enhancer

Epigenetic Inactivation of the Dioxin-Responsive Cytochrome P4501A1 Gene in Human Prostate Cancer

Conditional transgenic technologies

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