title: Transcriptional regulation of gene expression by microRNAs as endogenous decoys of transcription factors.
abstract: OBJECTIVE
  MicroRNAs (miRNAs) are known to produce post-transcriptional repression of gene expression. In light of the ability of decoy oligodeocynucleotides (ODNs) to sequestrate transcription factors (TFs) and the similar double-stranded structure between decoy ODNs and miRNAs, we proposed that miRNAs might act as endogenous decoy molecules to produce transcriptional regulation of gene expression.
  
  
  METHODS
  Quantitative real-time RT-PCR analysis was used to measure the changes of miRNA and mRNA expression. Luciferase reporter gene activity assay was used to investigate the functional interaction between miRNAs and TFs. Electrophoresis mobility shift assay (EMSA) and modified chromatin immunoprecipitation assay (ChIP) were utilized to investigate the physical interactions between miRNAs and TFs. MTT cell viability assay and cellular DNA fragmentation ELISA were used to study apoptotic cell death.
  
  
  RESULTS
  We presented here that miRNAs could regulate, either negatively or positively, gene expression at the transcriptional level through its decoy-like actions and this mechanism operates under physiological conditions to produce cellular functions. We identified the putative cis-elements for transcriptional factors NF-κB and NFAT in the mature miR-939 and miR-376a, respectively. We experimentally established the ability of these miRNAs to physically bind their respective target TFs, using EMSA and ChIP methods. We then utilized the luciferase reporter gene assay to characterize the specific regulation of luciferase gene activities by miR-939/pre-miR-939:NF-κB or miR-376a/pre-miR-376a:NFAT interactions. Moreover, miR-939 and miR-376a produced transcriptional regulation of endogenous genes Bcl-xL and FasL/miR-26 that are the transcriptional targets for NF-kB and NFAT, respectively, but are not post-transcriptional targets for these two miRNAs. Finally, interference of these miRNAs with NF-κB and NFAT demonstrated clear phenotypes at the cellular level as manifested by the regulation of neuroblastoma cell death by miR-939 and miR-376a.
  
  
  CONCLUSIONS
  Our study identified a novel non-canonical mechanism of miRNAs and suggests that when considering the cellular function of miRNAs the decoy-like mechanism for transcriptional regulation (activation or repression) should be taken into account.
authors.affiliation: Department of General Surgery, Zhujiang Hospital, Southern Medical University, Guangzhou, China.
authors.forename: Chunhui
authors.initials: C
authors.lastname: Cui
authors.forename: Jinlong
authors.initials: J
authors.lastname: Yu
authors.forename: Shuxin
authors.initials: S
authors.lastname: Huang
authors.forename: Huiquan
authors.initials: H
authors.lastname: Zhu
authors.forename: Zonghai
authors.initials: Z
authors.lastname: Huang
mesh_terms: D000818:Animals; D002460:Cell Line; D045744:Cell Line, Tumor; D047369:Chromatin Immunoprecipitation; D057809:HEK293 Cells; D006801:Humans; D035683:MicroRNAs / Q000235:genetics* / Q000378:metabolism; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism; D050778:NFATC Transcription Factors / Q000235:genetics / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000235:genetics*; D011485:Protein Binding; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism; D015533:Transcriptional Activation
chemical_list: C573498:MIRN376C microRNA, human; D035683:MicroRNAs; D016328:NF-kappa B; D050778:NFATC Transcription Factors; D014157:Transcription Factors