title: The role of microRNAs in hepatocyte nuclear factor-4alpha expression and transactivation.
abstract: Hepatocyte nuclear factor (HNF)-4α is a key member of the transcription factor network regulating hepatocyte differentiation and function. Genetic and molecular evidence suggests that expression of HNF-4α is mainly regulated at the transcriptional level. Activation of HNF-4A gene involves the interaction of distinct sets of transcription factors and co-transcription factors within enhancer and promoter regions. Here we study the inhibitory effect of microRNAs (miRNAs) on the 3'-untranslated region (3'-UTR) of HNF-4A mRNA. The potential recognition elements of a set of miRNAs were identified utilizing bioinformatics analysis. The family members of miR-34 and miR-449, including miR-34a, miR-34c-5p and miR-449a, share the same target elements located at two distinct locations within the 3'-UTR of HNF-4A. The over-expression of miR-34a, miR-34c-5p or miR-449a in HepG2 cells led to a significant decrease in the activity of luciferase reporter carrying 3'-UTR of HNF-4A. The repressive effect on reporter activity was partially or fully eliminated when one or two of the binding site(s) for miR-34a/miR-34c-5p/miR-449a were deleted within the 3'-UTR. The protein level of HNF-4α was dramatically reduced by over-expression of miR-34a, miR-34c-5p and miR-449a, which correlates with a decrease in the binding activity of HNF-4α and transactivation of HNF-4α target genes. These results suggest that the recognition sites of miR-34a, miR-34c-5p and miR-449a within 3'-UTR of HNF-4A are functional. The mechanism of down-regulation of the binding activity and transactivation of HNF-4α by the miRNAs involves the decrease in HNF-4α protein level via miRNAs selectively targeting HNF-4A 3'-UTR, leading to the translational repression of HNF-4α expression.
authors.affiliation: Department of Surgery, Boston University School of Medicine, Boston, MA 02118, USA.
authors.forename: Zhongyan
authors.initials: Z
authors.lastname: Wang
authors.forename: Peter A
authors.initials: PA
authors.lastname: Burke
mesh_terms: D020413:3' Untranslated Regions; D001665:Binding Sites; D045744:Cell Line, Tumor; D005786:Gene Expression Regulation; D051557:Hepatocyte Nuclear Factor 4 / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D035683:MicroRNAs / Q000378:metabolism*; D015533:Transcriptional Activation
chemical_list: D020413:3' Untranslated Regions; C496592:HNF4A protein, human; D051557:Hepatocyte Nuclear Factor 4; C522425:MIRN34 microRNA, human; C544530:MIRN449 microRNA, human; D035683:MicroRNAs