Characterization of the miRNAs Down-Regulating COX-2 and Survivin

miRNAs are a family of small, noncoding RNAs that regulate gene expression in a sequence-specific manner. miRNAs regulate gene expression by inhibiting translation or by targeting messenger RNA (mRNA) for degradation in a post-transcriptional fashion. The importance of miRNAs lies in the broad range of phenotypes they regulate including development, cell proliferation and death, apoptosis, cell differentiation. In this study, we attempted to screen and identify miRNAs which target the genes, which are related to inflammation, cell growth and cell cycle arrest, including cox-2 and survivin. To screen miRNAs regulating the gene expression, we first selected miRNA candidates that are predicted to target 3'-UTR of the genes by TargetScan program. Using the luciferase reporter assay, miRNAs down-regulating the gene expression was determined after co-transfection with miRNAs. The inhibitory effect of miRNAs was also examined by Western blot analysis and quantitative real-time PCR. The binding sites for the miRNAs in the 3’-UTR of the mRNA were determined by the luciferase reporter assay after mutagenesis of the predicted binding sites in the 3’-UTR. We could identify miRNAs, miR-199a, -145, - 542-3p, -543, -26a, down-regulating the expression of the genes for cox-2, and miR-542-3p down-regulating survivin.