title: The polypyrimidine/polypurine motif in the mouse mu opioid receptor gene promoter is a supercoiling-regulatory element.
abstract: The mu opioid receptor (MOR) is the principle molecular target of opioid analgesics. The polypyrimidine/polypurine (PPy/u) motif enhances the activity of the MOR gene promoter by adopting a non-B DNA conformation. Here, we report that the PPy/u motif regulates the processivity of torsional stress, which is important for endogenous MOR gene expression. Analysis by topoisomerase assays, S1 nuclease digests, and atomic force microscopy showed that, unlike homologous PPy/u motifs, the position- and orientation-induced structural strains to the mouse PPy/u element affect its ability to perturb the relaxation activity of topoisomerase, resulting in polypurine strand-nicked and catenated DNA conformations. Raman spectrum microscopy confirmed that mouse PPy/u containing-plasmid DNA molecules under the different structural strains have a different configuration of ring bases as well as altered Hoogsteen hydrogen bonds. The mouse MOR PPy/u motif drives reporter gene expression fortyfold more effectively in the sense orientation than in the antisense orientation. Furthermore, mouse neuronal cells activate MOR gene expression in response to the perturbations of topology by topoisomerase inhibitors, whereas human cells do not. These results suggest that, interestingly among homologous PPy/u motifs, the mouse MOR PPy/u motif dynamically responds to torsional stress and consequently regulates MOR gene expression in vivo.
authors.affiliation: The Department of Pharmacology, University of Minnesota Medical School, Minneapolis, MN 55455, USA.
authors.forename: Chung-youl
authors.initials: CY
authors.lastname: Choe
authors.forename: Hogyoung
authors.initials: H
authors.lastname: Kim
authors.forename: Jinping
authors.initials: J
authors.lastname: Dong
authors.forename: Andre J
authors.initials: AJ
authors.lastname: van Wijnen
authors.forename: Ping-Yee
authors.initials: PY
authors.lastname: Law
authors.forename: Horace H
authors.initials: HH
authors.lastname: Loh
mesh_terms: D000818:Animals; D001665:Binding Sites / Q000235:genetics; D002166:Camptothecin / Q000031:analogs & derivatives / Q000494:pharmacology; D045744:Cell Line, Tumor; D004247:DNA / Q000737:chemistry / Q000235:genetics*; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D000077146:Irinotecan; D008156:Luciferases / Q000235:genetics / Q000378:metabolism; D051379:Mice; D018625:Microscopy, Atomic Force; D009690:Nucleic Acid Conformation; D011401:Promoter Regions, Genetic / Q000235:genetics*; D011685:Purine Nucleotides / Q000737:chemistry / Q000235:genetics; D011742:Pyrimidine Nucleotides / Q000737:chemistry / Q000235:genetics; D017450:Receptors, Opioid, mu / Q000235:genetics* / Q000378:metabolism; D012045:Regulatory Sequences, Nucleic Acid / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013059:Spectrum Analysis, Raman; D059004:Topoisomerase I Inhibitors / Q000494:pharmacology
chemical_list: D011685:Purine Nucleotides; D011742:Pyrimidine Nucleotides; D017450:Receptors, Opioid, mu; D059004:Topoisomerase I Inhibitors; D000077146:Irinotecan; D004247:DNA; D008156:Luciferases; D002166:Camptothecin