MicroRNA-21 is upregulated during the proliferative phase of liver regeneration, targets Pellino-1, and inhibits NF-kappaB signaling.
During liver regeneration, normally quiescent liver cells reenter the cell cycle, nonparenchymal and parenchymal cells divide, and proper liver architecture is restored. The gene expression programs regulating these transitions are not completely understood. MicroRNAs are a newly discovered class of small regulatory RNAs that silence messenger RNAs by binding to their 3'-untranslated regions (UTRs). A number of microRNAs, including miR-21, have been shown to be involved in regulation of cell proliferation. We performed partial hepatectomies on mice and allowed the liver to regenerate for 1, 6, 12, 24, and 48 h and 4 and 7 days. We compared the expression of miR-21 in the posthepatectomy liver to the prehepatectomy liver by Northern blot and found that miR-21 was upregulated during the early stages of liver regeneration. NF-kappaB signaling is also activated very early during liver regeneration. It has been previously reported that NF-kappaB upregulates the miR-21 precursor transcript. The predicted miR-21 target, Pellino (Peli1), is a ubiquitin ligase involved in activating NF-kappaB signaling. We observed an inverse correlation between miR-21 and Peli1 mRNA levels during liver regeneration. miR-21 overexpression in cultured cells inhibited a Peli1 3'-UTR luciferase reporter. Using NF-kappaB reporter assays, we determined that miR-21 overexpression inhibits NF-kappaB signaling. In conclusion, miR-21 expression was upregulated during early stages of liver regeneration. Targeting of Peli1 by miR-21 could potentially provide the basis for a negative feedback cycle regulating NF-kappaB signaling.
Marquez
Rebecca T
RT
University of Iowa School of Medicine, Department of Internal Medicine, University of Iowa, Iowa City, Iowa 52242, USA.
Wendlandt
Erik
E
Galle
Courtney Searcey
CS
Keck
Kathy
K
McCaffrey
Anton P
AP
D020413:3' Untranslated Regions / Q000235:genetics; D000818:Animals; D002460:Cell Line; D015870:Gene Expression / Q000187:drug effects / Q000235:genetics; D005786:Gene Expression Regulation / Q000502:physiology*; D017930:Genes, Reporter / Q000235:genetics; D006801:Humans; D015850:Interleukin-6 / Q000235:genetics; D008070:Lipopolysaccharides / Q000494:pharmacology; D008115:Liver Regeneration / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D035683:MicroRNAs / Q000235:genetics / Q000378:metabolism*; D008954:Models, Biological; D009154:Mutation / Q000235:genetics; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism*; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D051197:Toll-Like Receptor 4 / Q000235:genetics / Q000378:metabolism; D014162:Transfection; D044767:Ubiquitin-Protein Ligases; D015854:Up-Regulation / Q000502:physiology*
D020413:3' Untranslated Regions; D015850:Interleukin-6; D008070:Lipopolysaccharides; C531950:MIRN21 microRNA, mouse; D035683:MicroRNAs; D016328:NF-kappa B; D009687:Nuclear Proteins; D051197:Toll-Like Receptor 4; C023023:lipid-linked oligosaccharides; D044767:Ubiquitin-Protein Ligases; C418046:Peli1 protein, mouse