1. School of Basic Medical Sciences, Xi'an Jiaotong University, Xi'an 710061, China.
2. Department of Chemistry, Korea University, Seoul 02841, Korea.
3. Engineering Research Center of Molecular and Neuro Imaging, Ministry of Education, School of Life Science and Technology, Xidian University, Xi'an 710071, China.
4. Xianyang Key Laboratory of Molecular Imaging and Drug Synthesis, School of Pharmacy, Shaanxi Institute of International Trade & Commerce, Xianyang 712046, Shaanxi, China.
Rationale: MicroRNAs (miRNAs) play key roles in multiple biological processes, many of which exhibit distinct cell type-specific expression patterns. A miRNA-inducible expression system can be adapted as a signal-on reporter for detecting miRNA activity or as a cell type-specific gene activation tool. However, due to the inhibitory properties of miRNAs on gene expression, few miRNA-inducible expression systems are available, and the available systems are only transcriptional or post-transcriptional regulatory system with obvious leaky expression.
Methods: To address this limitation, a miRNA-inducible expression system that can tightly control target gene expression is desirable. Here, by taking advantage of an enhanced LacI repression system and the translational repressor L7Ae, a miRNA-inducible dual transcriptional-translational switch system was designed called the miR-ON-D system. Luciferase activity assay, western blotting, CCK-8 assay and flow cytometry analysis were performed to characterize and validate this system.
Results: The results demonstrated that leakage expression was strongly suppressed in the miR-ON-D system. It was also validated that the miR-ON-D system could be used to detect exogenous and endogenous miRNAs in mammalian cells. Moreover, it was shown that the miR-ON-D system could be triggered by cell type-specific miRNAs to regulate the expression of biologically relevant proteins (e.g., p21 and Bax) to achieve cell type-specific reprogramming.
Conclusion: This study established a tight miRNA-inducible expression switch system for miRNA detection and cell type-specific gene activation.
Keywords: microRNAs, cell type-specific, gene regulation, p21, Bax