ABSTRACT
DNA methylation is an essential epigenetic modification involved in numerous biological processes. Here, we present a cell-based system pLTR-Luc2P-EGFP for evaluation of DNA methylation in mammalian cells. In this system, the expression of reporter gene luciferase2P (Luc2P)-EGFP is under the control of HIV-1 promoter 5' long terminal repeat (LTR), which contains multiple CpG sites. Once these sites are methylated, the expression of Luc2P-EGFP is turned off, which may be visualized under fluorescence microscopy, with quantification performed in luciferase activity assay. As a proof of principle, pLTR-Luc2P-EGFP was methylated in vitro, and transfected into 293T cells, where the reduction of Luc2P-EGFP expression was confirmed. Premixed reporter DNA samples with the methylation levels varying from 0 to 100% were used for quantitative measurements of DNA methylation. The resulting standard curves indicated the accuracy of luciferase activity exceeding that of the Western blotting against EGFP. The Bland-Altman analysis showed that data from luciferase activity assay were in good agreement with the actual DNA methylation levels. In summary, we have established a reporter system coupled with reliable detection technique capable of efficient quantifying the changes in methylation in mammalian cells. This system may be utilized as a high throughput screening tool for identifying molecules that modulate DNA methylation.
Subject(s)
DNA Methylation , Epigenesis, Genetic , Animals , Genes, Reporter , Luciferases/genetics , Promoter Regions, GeneticABSTRACT
DNA methylation is an essential epigenetic modification involved in numerous biological processes. Here, we present a cell-based system pLTR-Luc2P-EGFP for evaluation of DNA methylation in mammalian cells. In this system, the expression of reporter gene luciferase2P (Luc2P)-EGFP is under the control of HIV-1 promoter 5' long terminal repeat (LTR), which contains multiple CpG sites. Once these sites are methylated, the expression of Luc2P-EGFP is turned off, which may be visualized under fluorescence microscopy, with quantification performed in luciferase activity assay. As a proof of principle, pLTR-Luc2P-EGFP was methylated in vitro, and transfected into 293T cells, where the reduction of Luc2P-EGFP expression was confirmed. Premixed reporter DNA samples with the methylation levels varying from 0 to 100% were used for quantitative measurements of DNA methylation. The resulting standard curves indicated the accuracy of luciferase activity exceeding that of the Western blotting against EGFP. The Bland-Altman analysis showed that data from luciferase activity assay were in good agreement with the actual DNA methylation levels. In summary, we have established a reporter system coupled with reliable detection technique capable of efficient quantifying the changes in methylation in mammalian cells. This system may be utilized as a high throughput screening tool for identifying molecules that modulate DNA methylation.
ABSTRACT
Although the Mdm2/p53 interaction has been well documented, it is not clear whether there are new microRNAs participating in this regulatory network. Here, we provide evidence that miR-509-5p, which is downregulated in a subset of newly diagnosed cervical cancer and hepatocellular carcinoma tissues compared with the adjacent nontumor tissue, can be activated by p53 through binding the promoter of miR-509-5p and it suppresses the growth and invasion/migration of cervical cancer and hepatoma cells by regulating apoptosis and the G1/S-phase transition of cell cycle. Furthermore, Mdm2 was identified to be a target of miR-509-5p by targeting its 3'-UTR. Restoration of Mdm2 abrogated the cell phenotypes induced by miR-509-5p. Moreover, ectopic expression of miR-509-5p in HeLa and QGY-7703 cells repressed the expression of Mdm2, subsequently enhancing its p53-activating effects. These results suggest that miR-509-5p is a new regulator of Mdm2/p53 pathway and may play a key role in cancer development.
