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Báo cáo khoa học: The influence of heterodimer partner ultraspiracle/retinoid X receptor on the function of ecdysone receptor
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A pair of nuclear receptors, ecdysone receptor (EcR) and ultraspiracle (USP), heterodimerize and transduce ecdysteroid signals. The EcR and its nonsteroidal ligands are being developed for regulation of transgene expres-sion in humans, animals and plants. In mammalian cells, EcR:USP heterodimers can function in the absence of ligand, but EcR⁄retinoid X receptor (EcR:RXR) heterodimers require the presence of ligand for activa-tion. | ềFEBS Journal The influence of heterodimer partner ultraspiracle retinoid X receptor on the function of ecdysone receptor Subba R. Palli1 Mariana Z. Kapitskaya2 and David W. Potter2 1 Department of Entomology University of Kentucky Lexington KY USA 2 RheoGene Inc. Norristown PA USA Keywords gene switch ligand-binding domain nuclear receptor steroid hormone Correspondence S. R. Palli Department of Entomology S225 Agricultural Science Center College of Agriculture University of Kentucky Lexington KY 40546 USA E-mail rpalli@uky.edu Received 14 July 2005 revised 26 August 2005 accepted 3 October 2005 doi 10.1111 j.1742-4658.2005.05003.x A pair of nuclear receptors ecdysone receptor EcR and ultraspiracle USP heterodimerize and transduce ecdysteroid signals. The EcR and its nonsteroidal ligands are being developed for regulation of transgene expression in humans animals and plants. In mammalian cells EcR USP heterodimers can function in the absence of ligand but EcR retinoid X receptor EcR RXR heterodimers require the presence of ligand for activation. The heterodimer partner of EcR can influence ligand sensitivity of EcR so that the EcR Locusta migratoria RXR EcR LmRXR heterodimers are activated at lower concentrations of ligand when compared with the concentrations of ligand required for the activation of EcR Homo sapiens RXR EcR HsRXR heterodimers. Analysis of chimeric RXRs containing regions of LmRXR and HsRXR and point mutants of HsRXR showed that the amino acid residues present in helix 9 and in the two loops on either end of helix 9 are responsible for improved activity of LmRXR. The EcR Lm-HsRXR chimera heterodimer induced reporter genes with nanomolar concentration of ligand compared with the micromolar concentration of ligand required for activating the EcR HsRXR heterodimer. The EcR Lm-HsRXR chimera heterodimer but not the EcR HsRXR heterodimer supported ligand-dependent induction of reporter gene in a C57BL 6 mouse model. Steroid hormones ecdysteroids .