RT Journal Article SR Electronic T1 In Silico and In Vitro Identification of MicroRNAs That Regulate Hepatic Nuclear Factor 4α Expression JF Drug Metabolism and Disposition JO Drug Metab Dispos FD American Society for Pharmacology and Experimental Therapeutics SP 726 OP 733 DO 10.1124/dmd.111.040329 VO 40 IS 4 A1 Anuradha Ramamoorthy A1 Lang Li A1 Andrea Gaedigk A1 L. DiAnne Bradford A1 Eric A. Benson A1 David A. Flockhart A1 Todd C. Skaar YR 2012 UL http://dmd.aspetjournals.org/content/40/4/726.abstract AB Hepatic nuclear factor 4α (HNF4A) is a nuclear transcription factor that regulates the expression of many genes involved in drug disposition. To identify additional molecular mechanisms that regulate HNF4A, we identified microRNAs (miRNAs) that target HNF4A expression. In silico analyses suggested that HNF4A is targeted by many miRNAs. We conducted in vitro studies to validate several of these predictions. With use of an HNF4A 3′-untranslated region (UTR) luciferase reporter assay, five of six miRNAs tested significantly down-regulated (∼20–40%) the luciferase activity. In HepG2 cells, miR-34a and miR-449a also down-regulated the expression of both the HNF4A protein and an HNF4A target gene, PXR (∼30–40%). This regulation appeared without reduction in HNF4A mRNA expression, suggesting that they must be blocking HNF4A translation. Using additional bioinformatic algorithms, we identified polymorphisms that are predicted to alter the miRNA targeting of HNF4A. Luciferase assays indicated that miR-34a and miR-449a were less effective in regulating a variant (rs11574744) than the wild-type HNF4A 3′-UTR. In vivo, subjects with the variant HNF4A had lower CYP2D6 enzyme activity, although this result was not statistically significant (p = 0.16). In conclusion, our findings demonstrate strong evidence for a role of miRNAs in the regulation of HNF4A.