RT Journal Article SR Electronic T1 The Long Non-coding RNA HNF4A-AS1 Negatively Regulates Cytochrome P450 Enzymes in Huh7 Cells via Histone Modifications JF Drug Metabolism and Disposition JO Drug Metab Dispos FD American Society for Pharmacology and Experimental Therapeutics SP DMD-AR-2020-000316 DO 10.1124/dmd.120.000316 A1 Pei Wang A1 Shitong Chen A1 Yiting Wang A1 Xiaofei Wang A1 Liang Yan A1 Kun Yang A1 Xiao-bo Zhong A1 Shengna Han A1 Lirong Zhang YR 2021 UL http://dmd.aspetjournals.org/content/early/2021/03/05/dmd.120.000316.abstract AB The maintenance of homeostasis of cytochrome P450s (CYPs) under both physiological and xenobiotic exposure conditions is ensured by the action of positive and negative regulators. In the current study, the hepatocyte nuclear factor 4 alpha (HNF4A) antisense RNA 1 (HNF4A-AS1), an antisense lncRNA of HNF4A, was found to be a negative regulator of the basal and rifampicin (RIF)-induced expression of nuclear receptors and downstream CYPs. In Huh7 cells, knockdown of HNF4A-AS1 resulted in elevated expression of HNF4A, pregnane X receptor (PXR), and CYPs (including CYP3A4) under both basal and RIF-induced conditions. Conversely, overexpression of HNF4A-AS1 led to decreased basal expression of constitutive androstane receptor (CAR), aryl hydrocarbon receptor (AHR), PXR, and all studied CYPs. Of note, significantly diminished induction levels of PXR, CYP1A2, 2C8, 2C19, and 3A4 by RIF were also observed in HNF4A-AS1 plasmid transfected Huh7 cells. Moreover, the negative feedback of HNF4A on HNF4A-AS1 mediated gene expression was validated using a loss-of-function experiment in this study. Strikingly, our data showed that increased enrichment levels of histone 3 lysine 4 timethylation (H3K4me3) and HNF4A in the CYP3A4 promoter contribute to the elevated CYP3A4 expression after HNF4A-AS1 knockdown. Overall, the current study reveals that histone modifications contribute to the negative regulation of nuclear receptors and CYPs by HNF4A-AS1 in basal and drug-induced levels. Significance Statement Utilizing loss-of-function and gain-of-function experiments, the current study systematically investigated the negative regulation of HNF4A-AS1 on the expression of nuclear receptors (including HNF4A, CAR, AHR, and PXR) and CYPs (including CYP1A2, 2E1, 2B6, 2D6, 2C8, 2C9, 2C19, and 3A4) in both basal and RIF-induced levels in Huh7 cells. Notably, this study is the first to reveal the contribution of histone modification to the HNF4A-AS1 mediated expression of CYP3A4 in Huh7 cells.