In Vivo Visualization of RNAi Efficiency Using a Pumilio/FBF Protein-Based Reporter

As a strategy that induces gene silencing by the delivery of small interfering RNA (siRNA) targeting a specific gene locus into cells or tissues, RNA interference (RNAi) technology holds the potential to be a powerful tool in a range of intractable disorder therapeutics. However, reliable noninvasive probes for visualizing the siRNA delivery and silencing efficiency have become a major obstacle in siRNA-based treatment. Here, we describe the development of an RNA-binding protein Pumilio/FBF (PUF)-based reporter probe for the monitoring of siRNA delivery efficiency and functional screening of effective siRNA target sites in vivo. This reporter consisted of a Firefly luciferase (Fluc) gene whose expression is regulated by the unique interaction architecture of the PUF protein with its Nanos response element (NRE) target RNA. We showed that a robust and rapid increase in the luminescence signal was detected by the successful delivery of siRNA against the enhanced green fluorescent protein (EGFP) or p53 genes into mammalian cells or the livers of mice. The delivery efficiencies of various commercial transfection vehicles were quantitatively evaluated with this reporter. In addition, we also employed in vivo bioluminescence imaging to screen and identify the most potent siRNA targeting p53. Our study indicates that the positive-readout reporter represents a promising indicator for siRNA optimization and visualization, advancing the development of siRNA therapeutic products.