Project description:To confirme the difference of target supression effect, we transfected non-methylated micro RNA or methylated microRNA in DICER knockout HCT116 cell.
Project description:To confirme the function of methylated micro RNAs (miR-17 and let-7a), we transfected methylated or non-methylated microRNAs to DICER KO HCT116 cell line. mRNA were isolated at 48 houes after transfection. This data show that the function were different between methylated or non-methylated microRNAs.
Project description:Little is known about how miRNAs are turned over, in particular in mammalian cells. A target-dependent miRNA degradation mechanism (TDMD) has been recently suggested, in which RNA targets may induce miRNA degradation. However, endogenous RNA targets involved in TDMD have not been yet identified. During serum stimulation of quiescent fibroblasts, a deep change of miRNA expression occurs in few hours. We scanned the mammalian genome for targets eligible for TDMD and found a dominant miRNA:target pair, consisting of a target (SerpinE1) extraordinarily induced upon serum stimulation and two matched miRNAs (miR-30b/c) quickly downregulated. We verified directly the occurrence of TDMD by interfering specifically with the miR-:target interaction, keeping target and miRNA expression at endogenous levels, using CRISPR/cas9 mediated deletion of the miR-30 responsive element (MRE) of SerpinE1. In MRE-KO cells, we observed the stabilization of the predicted miRNAs, with no evidence of alterations in precursors or unrelated miRNAs, suggesting that TDMD is occurring and has been disrupted by a single MRE deletion. At molecular level miRNA degradation occurs within physiological ranges of target expression (upon 1000 copies per cells) and is accompanied by modification on 3’ends (tailing, mostly through adenylation). TDMD suppression was sufficient to shift the activity of miR-30b/c towards other shared targets, modulate significantly gene expression and, thus, influence cellular functions, including cell proliferation, apoptosis, and adhesion. In conclusion, these data strongly support the existence of a novel and sophisticated regulatory layer of miRNA and gene expression mediated by specific endogenous targets in mammalian cells.
Project description:Recent studies have reported that competitive endogenous RNAs (ceRNAs) can act as sponges for a miRNA through their binding sites and that changes in ceRNA abundances from individual genes can modulate the miRNA’s activity. Consideration of this hypothesis would benefit from knowing the quantitative relationship between a miRNA and its endogenous target sites. Here, we altered intracellular target-site abundance through expression of a miR-122 target in hepatocytes and livers, and analyzed the effects on miR-122 target genes. Target repression was released in a threshold-like manner at high target-site abundance (≥1.5x10^5 added target sites per cell), and this threshold was insensitive to the effective levels of the miRNA. Furthermore, in response to extreme metabolic liver disease models, global target-site abundance of hepatocytes did not change sufficiently to affect miRNA-mediated repression. Thus, modulation of miRNA target abundance is unlikely to cause significant effects on gene expression and metabolism through a ceRNA effect.