Journal ArticleDOI
The orphan human pregnane X receptor mediates the transcriptional activation of CYP3A4 by rifampicin through a distal enhancer module.
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TLDR
The results provide evidence for the existence of a potent enhancer module, 8 kb distal to the transcription start point, which mediates the transcriptional induction of CYP3A4 by activators of hPXR and demonstrate cooperativity between elements within the distal enhancer region and cis-acting elements in the proximal promoter of CYp3A 4.Abstract:
Cytochrome P-450 3A4 (CYP3A4), the predominant cytochrome P-450 expressed in adult human liver, is subject to transcriptional induction by a variety of structurally unrelated xenobiotics, including the antibiotic rifampicin. The molecular mechanisms underlying this phenomenon are poorly understood. We transfected a human liver-derived cell line (HepG2) with various CYP3A4 -luciferase reporter gene constructs containing a nested set of 5′-deletions of the CYP3A4 5′-flanking region. Rifampicin-inducible transcription of the reporter gene was observed only with the longest construct, which encompassed bases −13000 to +53 of CYP3A4 (3-fold induction). The responsive region was functional regardless of its position or orientation relative to the proximal promoter of CYP3A4 and was capable of conferring rifampicin-inducible expression on a heterologous promoter. Further deletion mutants localized the induction to bases −7836 to −7607. In vitro DNase I footprint analysis of this region revealed four protected sites (FP1, FP2, FP3, and FP4). Two of these sites, FP3 (bases −7738 to −7715) and FP4 (bases −7698 to −7682), overlapped binding motifs for the orphan human pregnane X receptor (hPXR). Cotransfection of responsive constructs with a hPXR expression vector substantially increased the rifampicin-inducibility to ∼50-fold. In addition, the rifampicin-responsive constructs were strongly activated by a range of CYP3A inducers. Finally, we demonstrate cooperativity between elements within the distal enhancer region and cis -acting elements in the proximal promoter of CYP3A4 . Our results provide evidence for the existence of a potent enhancer module, 8 kb distal to the transcription start point, which mediates the transcriptional induction of CYP3A4 by activators of hPXR.read more
Citations
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Journal ArticleDOI
Sequence diversity in CYP3A promoters and characterization of the genetic basis of polymorphic CYP3A5 expression.
Peter M. Kuehl,Jiong Zhang,Yvonne S. Lin,Jatinder K. Lamba,Mahfoud Assem,John D. Schuetz,Paul B. Watkins,Ann K. Daly,Steven A. Wrighton,Stephen D. Hall,Patrick Maurel,Mary V. Relling,Cynthia Brimer,Kazuto Yasuda,Raman Venkataramanan,Stephen C. Strom,Kenneth E. Thummel,Mark S. Boguski,Erin G. Schuetz +18 more
TL;DR: CYP3A5 was more frequently expressed in livers of African Americans than in those of Caucasians, and may be the most important genetic contributor to interindividual and interracial differences in CYP3A-dependent drug clearance and in responses to many medicines.
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The challenge of new drug discovery for tuberculosis
TL;DR: In this review, innovations in TB drug discovery and evolving strategies to bring newer agents more quickly to patients are discussed.
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Genetic contribution to variable human CYP3A-mediated metabolism
TL;DR: The human CYP3A subfamily plays a dominant role in the metabolic elimination of more drugs than any other biotransformation enzyme and may be implicated in disease risk and the metabolism of endogenous steroids or xenobiotics in these tissues.
Journal ArticleDOI
Regulation of multidrug resistance-associated protein 2 (ABCC2) by the nuclear receptors pregnane X receptor, farnesoid X-activated receptor, and constitutive androstane receptor
Heidi Rachelle Kast,Bryan Goodwin,Paul T. Tarr,Stacey A. Jones,Andrew M. Anisfeld,Catherine M. Stoltz,Peter Tontonoz,Steve A. Kliewer,Timothy M. Willson,Peter A. Edwards,Peter A. Edwards +10 more
TL;DR: It is demonstrated that MRP2 is regulated by three distinct nuclear receptor signaling pathways that converge on a common response element in the 5′-flanking region of this gene.
Journal ArticleDOI
The nuclear pregnane X receptor: a key regulator of xenobiotic metabolism.
TL;DR: Although PXR evolved to protect the body, its activation by a variety of prescription drugs represents the molecular basis for an important class of harmful drug-drug interactions, so assays that detect PxR activity will be useful in developing safer prescription drugs.
References
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TL;DR: Molecular Cloning has served as the foundation of technical expertise in labs worldwide for 30 years as mentioned in this paper and has been so popular, or so influential, that no other manual has been more widely used and influential.
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Molecular mechanisms of action of steroid/thyroid receptor superfamily members
Ming-Jer Tsai,Bert W. O'Malley +1 more
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P450 superfamily: Update on new sequences, gene mapping, accession numbers and nomenclature
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