Eptor coactivator For correspondence: Kouichi Yoshinari, [email protected]; Ryota Shizu, [email protected] (SRC1, also known as NCOA1) or peroxisome proliferatoractivated receptor gamma coactivator 1 (PGC1), and induce the transcription of their target genes (four, five). Ligand binding to the ligand-binding domain (LBD) of nuclear receptors constitutes the initial step in target gene regulation. All nuclear receptor LBDs share the identical conserved 12 -helix architecture. In this context, the C-terminal helix 12 (H12), termed activation function 2 (AF2), inside the LBDs plays a key part in gene regulation by recruiting coregulators. Structural research have shown that the configuration of AF2 alters depending on ligand binding, and this agonist binding-dependent conformational alteration enables the receptor to recruit its MMP-13 review coactivators (six, 7). In contrast, antagonist binding to the LBD prevents AF2 from adopting the active stabilized conformation and induces the recruitment of corepressors. Pregnane X receptor (PXR), encoded by NR1I2 in humans, is usually a nuclear receptor that’s highly expressed within the liver and activated by numerous compounds which includes drugs, food ingredients, and pesticides. Ligand binding to PXR causes it to translocate in the cytoplasm for the nucleus to induce the transcription of genes encoding drug-metabolizing enzymes such as cytochrome P450s and drug transporters (eight, 9). Given that PXR activation enhances xenobiotic metabolism and disposition, it might bring about drug rug or drug ood interactions. Hence, PXR activation by exogenous chemical substances has been extensively studied for drug development and food and chemical safety (ten, 11). Traditionally, chemical activation of PXR is assessed by cellbased reporter gene assays and/or by figuring out the mRNA levels of PXR target genes, for example CYP3A4, in hepatocytes. More recently, in vitro high-throughput screening strategies utilizing recombinant proteins, such as time-resolved fluorescence resonance power transfer (TR-FRET) (12, 13), fluorescence polarization/anisotropy (14), isothermal titration calorimetry (15), hydrogen-deuterium exchange (16, 17), differential scanning fluorometry (18), and surface plasmon resonance (19), have already been applied. Most of these not too long ago created screening systems are determined by the ligand-bindingdependent conformational changes from the LBD, particularly the conformational changes of AF2. For high-throughput screening, understanding the conformational adjustments in ligand-activated nuclear receptors in detail is expected.J. Biol. Chem. (2021) 297(three)2021 THE AUTHORS. Published by Elsevier Inc on behalf of American Society for Biochemistry and Molecular Biology. This can be an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).Building of ligand-sensitive pregnane X receptorAlthough PXR is really a ligand-activated nuclear receptor, it’s reported that PXR has constitutive transcriptional activity no matter ligand binding, and its ligands regulate the localization of PXR from the cytoplasm to the nucleus (8, 20). It is actually well-known that RSK4 Accession transient expression of PXR in cultured cells induces constitutive nuclear localization and upregulates the transcription of target genes within the absence of any ligand (21). This ligand-independent basal activity just isn’t observed in other ligand-activated nuclear receptors, for instance retinoicacid-activated RXR, peroxisome proliferator-activated receptor gamma (PPAR), and vitamin D receptor (.