title: Epigenetic regulation of MicroRNA-122 by peroxisome proliferator activated receptor-gamma and hepatitis b virus X protein in hepatocellular carcinoma cells.
abstract: MicroRNA-122 (miR-122), a pivotal liver-specific miRNA, has been implicated in several liver diseases including hepatocellular carcinoma (HCC) and hepatitis C and B viral infection. This study aimed to explore epigenetic regulation of miR-122 in human HCC cells and to examine the effect of hepatitis C virus (HCV) and hepatitis B virus (HBV). We performed microRNA microarray analysis and identified miR-122 as the most up-regulated miRNA (6-fold) in human HCC cells treated with 5'aza-2'deoxycytidine (5-Aza-CdR, DNA methylation inhibitor) and 4-phenylbutyric acid (PBA, histone deacetylation inhibitor). Real-time polymerase chain reaction (PCR) analysis verified significant up-regulation of miR-122 by 5'aza and PBA in HCC cells, and to a lesser extent in primary hepatocytes. Peroxisome proliferator activated receptor-gamma (PPARγ) and retinoid X receptor alpha (RXRα) complex was found to be associated with the DR1 and DR2 consensus site in the miR-122 gene promoter which enhanced miR-122 gene transcription. 5-Aza-CdR and PBA treatment increased the association of PPARγ/RXRα, but decreased the association of its corepressors (N-CoR and SMRT), with the miR-122 DR1 and DR2 motifs. The aforementioned DNA-protein complex also contains SUV39H1, an H3K9 histone methyl transferase, which down-regulates miR-122 expression.
  
  
  CONCLUSIONS
  These findings establish a novel role of the PPARγ binding complex for epigenetic regulation of miR-122 in human HCC cells. Moreover, we show that hepatitis B virus X protein binds PPARγ and inhibits the transcription of miR-122, whereas hepatitis C viral particles exhibited no significant effect; these findings provide mechanistic insight into reduction of miR-122 in patients with HBV but not with HCV infection.
authors.affiliation: Department of Pathology and Laboratory Medicine, Tulane University School of Medicine, New Orleans, LA.
authors.forename: Kyoungsub
authors.initials: K
authors.lastname: Song
authors.forename: Chang
authors.initials: C
authors.lastname: Han
authors.forename: Jinqiang
authors.initials: J
authors.lastname: Zhang
authors.forename: Dongdong
authors.initials: D
authors.lastname: Lu
authors.forename: Srikanta
authors.initials: S
authors.lastname: Dash
authors.forename: Mark
authors.initials: M
authors.lastname: Feitelson
authors.forename: Kyu
authors.initials: K
authors.lastname: Lim
authors.forename: Tong
authors.initials: T
authors.lastname: Wu
mesh_terms: D001374:Azacitidine / Q000031:analogs & derivatives / Q000494:pharmacology; D006528:Carcinoma, Hepatocellular / Q000209:etiology / Q000235:genetics*; D000077209:Decitabine; D044127:Epigenesis, Genetic; D056945:Hep G2 Cells; D006526:Hepatitis C / Q000150:complications; D006801:Humans; D008113:Liver Neoplasms / Q000209:etiology / Q000235:genetics*; D008780:Methyltransferases / Q000502:physiology; D035683:MicroRNAs / Q000235:genetics / Q000502:physiology*; D047495:PPAR gamma / Q000502:physiology*; D010654:Phenylbutyrates / Q000494:pharmacology; D011401:Promoter Regions, Genetic; D012097:Repressor Proteins / Q000502:physiology; D015534:Trans-Activators / Q000502:physiology*; D054334:Viral Regulatory and Accessory Proteins
chemical_list: C531907:MIRN122 microRNA, human; D035683:MicroRNAs; D047495:PPAR gamma; D010654:Phenylbutyrates; D012097:Repressor Proteins; D015534:Trans-Activators; D054334:Viral Regulatory and Accessory Proteins; C057628:hepatitis B virus X protein; D000077209:Decitabine; C075773:4-phenylbutyric acid; C407843:SUV39H1 protein, human; D008780:Methyltransferases; D001374:Azacitidine