title: The micro-ribonucleic acid (miRNA) miR-206 targets the human estrogen receptor-alpha (ERalpha) and represses ERalpha messenger RNA and protein expression in breast cancer cell lines.
abstract: Micro-RNAs are small noncoding RNAs, which diminish the stability and/or translation of mRNAs. This study examined whether miR-206, previously shown to be elevated in estrogen receptor (ER)alpha-negative breast cancer, regulates the expression of ERalpha. Two putative miR-206 sites, (hERalpha1 and hERalpha2), were found in silico within the 3'-untranslated region of human ERalpha mRNA. Transfection of MCF-7 cells with pre-miR-206 or 2'-O-methyl antagomiR-206 specifically decreased or increased, respectively, ERalpha mRNA levels. Overexpression of pre-miR-206 reduced ERalpha and beta-actin protein levels, with no effect on ERbeta, E-cadherin, or glyceraldehyde-3-phosphate dehydrogenase. Reporter constructs containing the hERalpha1 or hERalpha2 binding sites inserted into the 3'-untranslated region of the luciferase mRNA conferred a 1.6- and 2.2-fold repression of luciferase activity, respectively, in HeLa cells. Both miR-206 sites responded accordingly to exogenous hsa-pre-miR-206 and 2'-O-methyl antagomiR-206, and both sites were rendered inactive by mutations that disrupted hybridization to the 5'-seed of miR-206. A C-->T single nucleotide polymorphism in the hERalpha1 site increased repression of luciferase activity to approximately 3.3-fold in HeLa cells. MiR-206 levels were higher in ERalpha-negative MB-MDA-231 cells than ERalpha-positive MCF-7 cells, but only the ERalpha1 site mediated significantly more repression in reporter constructs. MiR-206 expression was strongly inhibited by ERalpha agonists, but not by an ERbeta agonist or progesterone, indicating a mutually inhibitory feedback loop. These findings provide the first evidence for the posttranscriptional regulation of ERalpha by a micro-RNA in the context of breast cancer.
authors.affiliation: Department of Cell Biology, University of Connecticut Health Center, 263 Farmington Avenue, Farmington, Connecticut 06030, USA.
authors.forename: Brian D
authors.initials: BD
authors.lastname: Adams
authors.forename: Henry
authors.initials: H
authors.lastname: Furneaux
authors.forename: Bruce A
authors.initials: BA
authors.lastname: White
mesh_terms: D020413:3' Untranslated Regions; D001483:Base Sequence; D001943:Breast Neoplasms; D045744:Cell Line, Tumor; D047628:Estrogen Receptor alpha / Q000235:genetics*; D005260:Female; D005786:Gene Expression Regulation; D006367:HeLa Cells; D006801:Humans; D035683:MicroRNAs / Q000737:chemistry / Q000235:genetics*; D008969:Molecular Sequence Data; D009363:Neoplasm Proteins / Q000235:genetics; D009690:Nucleic Acid Conformation; D020641:Polymorphism, Single Nucleotide; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000235:genetics*; D014158:Transcription, Genetic
chemical_list: D020413:3' Untranslated Regions; D047628:Estrogen Receptor alpha; D035683:MicroRNAs; D009363:Neoplasm Proteins; D012333:RNA, Messenger