title: Transcriptional activation of microRNA-34a by NF-kappa B in human esophageal cancer cells.
abstract: BACKGROUND
  miR-34a functions as an important tumor suppressor during the process of carcinogenesis. However, the mechanism of miR-34a dysregulation in human malignancies has not been well elucidated. Our study aimed to further investigate the regulation mechanism of miR-34a.
  
  
  RESULTS
  We found that overexpression of NF-kappa B p65 subunit could increase miR-34a levels in EC109, an esophageal squamous cancer cell line, while ectopic expression of DN IkappaB leaded to a significant reduction of miR-34a expression. Bioinformatics analysis suggested three putative KB sites in promoter region of miR-34a gene. Mutation two of these KB sites impaired p65 induced miR-34a transcriptional activity. Chromatin immunoprecipitation and electrophoretic mobility shift assays both showed that NF-kappaB could specifically bind to the third KB site located in miR-34a promoter. In addition, we found that overexpression of NF-kappaB p65 could not successfully induce miR-34a expression in esophageal cancer cell lines with mutant p53 or decreased p53. Reporter assay further showed that NF-kappaB-induced miR-34a transcriptional activity was reduced by p53 impairment. Nevertheless, CHIP analysis suggested binding of NF-kappaB to miR-34a promoter was not affected in cells with mutant p53.
  
  
  CONCLUSIONS
  Our work indicates a novel mechanism of miR-34a regulation that NF-kappaB could elevate miR-34a expression levels through directly binding to its promoter. And wildtype p53 is responsible for NF-kappaB-mediated miR-34a transcriptional activity but not for NF-kappaB binding. These findings might be helpful in understanding miR-34a abnormality in human malignancies and open new perspectives for the roles of miR-34a and NF-kappaB in tumor progression.
authors.affiliation: Department of Medical Genetics, College of Basic Medicine, Third Military Medical University, Chongqing, People's Republic of China.
authors.forename: Juan
authors.initials: J
authors.lastname: Li
authors.forename: Kai
authors.initials: K
authors.lastname: Wang
authors.forename: Xuedan
authors.initials: X
authors.lastname: Chen
authors.forename: Hui
authors.initials: H
authors.lastname: Meng
authors.forename: Min
authors.initials: M
authors.lastname: Song
authors.forename: Yan
authors.initials: Y
authors.lastname: Wang
authors.forename: Xueqing
authors.initials: X
authors.lastname: Xu
authors.forename: Yun
authors.initials: Y
authors.lastname: Bai
mesh_terms: D001483:Base Sequence; D045744:Cell Line, Tumor; D004938:Esophageal Neoplasms / Q000201:enzymology / Q000235:genetics; D005786:Gene Expression Regulation; D006801:Humans; D035683:MicroRNAs / Q000378:metabolism*; D009154:Mutation; D016328:NF-kappa B / Q000235:genetics* / Q000378:metabolism; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D051996:Transcription Factor RelA / Q000235:genetics / Q000378:metabolism; D015533:Transcriptional Activation; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism
chemical_list: C522425:MIRN34 microRNA, human; D035683:MicroRNAs; D016328:NF-kappa B; D051996:Transcription Factor RelA; D016159:Tumor Suppressor Protein p53