title: Epigenetic silencing of miR-181c by DNA methylation in glioblastoma cell lines.
abstract: BACKGROUND
  Post-transcriptional regulation by microRNAs is recognized as one of the major pathways for the control of cellular homeostasis. Less well understood is the transcriptional and epigenetic regulation of genes encoding microRNAs. In the present study we addressed the epigenetic regulation of the miR-181c in normal and malignant brain cells.
  
  
  METHODS
  To explore the epigenetic regulation of the miR-181c we evaluated its expression using RT-qPCR and the in vivo binding of the CCCTC-binding factor (CTCF) to its regulatory region in different glioblastoma cell lines. DNA methylation survey, chromatin immunoprecipitation and RNA interference assays were used to assess the role of CTCF in the miR-181c epigenetic silencing.
  
  
  RESULTS
  We found that miR-181c is downregulated in glioblastoma cell lines, as compared to normal brain tissues. Loss of expression correlated with a notorious gain of DNA methylation at the miR-181c promoter region and the dissociation of the multifunctional nuclear factor CTCF. Taking advantage of the genomic distribution of CTCF in different cell types we propose that CTCF has a local and cell type specific regulatory role over the miR-181c and not an architectural one through chromatin loop formation. This is supported by the depletion of CTCF in glioblastoma cells affecting the expression levels of NOTCH2 as a target of miR-181c.
  
  
  CONCLUSIONS
  Together, our results point to the epigenetic role of CTCF in the regulation of microRNAs implicated in tumorigenesis.
authors.affiliation: Instituto de Fisiología Celular, Departamento de Genética Molecular, Universidad Nacional Autónoma de México, Ciudad de México, México.
authors.forename: Erandi
authors.initials: E
authors.lastname: Ayala-Ortega
authors.affiliation: Instituto de Fisiología Celular, Departamento de Genética Molecular, Universidad Nacional Autónoma de México, Ciudad de México, México.
authors.forename: Rodrigo
authors.initials: R
authors.lastname: Arzate-Mejía
authors.affiliation: Instituto de Fisiología Celular, Departamento de Genética Molecular, Universidad Nacional Autónoma de México, Ciudad de México, México.
authors.forename: Rosario
authors.initials: R
authors.lastname: Pérez-Molina
authors.affiliation: Instituto de Fisiología Celular, Departamento de Genética Molecular, Universidad Nacional Autónoma de México, Ciudad de México, México.
authors.forename: Edgar
authors.initials: E
authors.lastname: González-Buendía
authors.affiliation: Instituto de Fisiología Celular, Departamento de Genética Molecular, Universidad Nacional Autónoma de México, Ciudad de México, México.
authors.forename: Karin
authors.initials: K
authors.lastname: Meier
authors.affiliation: Instituto de Fisiología Celular, Departamento de Genética Molecular, Universidad Nacional Autónoma de México, Ciudad de México, México.
authors.forename: Georgina
authors.initials: G
authors.lastname: Guerrero
authors.affiliation: Instituto de Fisiología Celular, Departamento de Genética Molecular, Universidad Nacional Autónoma de México, Ciudad de México, México. frecilla@ifc.unam.mx.
authors.forename: Félix
authors.initials: F
authors.lastname: Recillas-Targa
mesh_terms: D014408:Biomarkers, Tumor / Q000096:biosynthesis* / Q000235:genetics; D000076246:CCCTC-Binding Factor; D045744:Cell Line, Tumor; D019175:DNA Methylation / Q000235:genetics; D044127:Epigenesis, Genetic; D015972:Gene Expression Regulation, Neoplastic; D020868:Gene Silencing; D005909:Glioblastoma / Q000235:genetics* / Q000473:pathology; D006801:Humans; D035683:MicroRNAs / Q000096:biosynthesis*; D051883:Receptor, Notch2 / Q000096:biosynthesis* / Q000235:genetics; D012097:Repressor Proteins / Q000096:biosynthesis* / Q000235:genetics
chemical_list: D014408:Biomarkers, Tumor; D000076246:CCCTC-Binding Factor; C000619697:CTCF protein, human; C000608460:MIRN-181 microRNA, human; D035683:MicroRNAs; C497764:NOTCH2 protein, human; D051883:Receptor, Notch2; D012097:Repressor Proteins
keywords: CCCTC-binding factor (CTCF); DNA methylation; Epigenetics; Glioblastoma cells; RNA interference