Transcriptional Activation of microRNA-34a by NF-kappa B in Human Esophageal Cancer Cells

BMC Mol Biol. 2012 Jan 31;13:4. doi: 10.1186/1471-2199-13-4.

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Base Sequence
  • Cell Line, Tumor
  • Esophageal Neoplasms / enzymology
  • Esophageal Neoplasms / genetics
  • Gene Expression Regulation
  • Humans
  • MicroRNAs / metabolism*
  • Mutation
  • NF-kappa B / genetics*
  • NF-kappa B / metabolism
  • Promoter Regions, Genetic
  • Protein Binding
  • Transcription Factor RelA / genetics
  • Transcription Factor RelA / metabolism
  • Transcriptional Activation*
  • Tumor Suppressor Protein p53 / genetics
  • Tumor Suppressor Protein p53 / metabolism

Substances

  • MIRN34 microRNA, human
  • MicroRNAs
  • NF-kappa B
  • Transcription Factor RelA
  • Tumor Suppressor Protein p53