Engineering of a promoterless anti-viral RNAi hairpin into an endogenous miRNA locus [miRNA]

Short hairpin RNA (shRNA) expression strategies that allow safe and persistent target mRNA knockdown are key to the success of many in vitro or in vivo RNAi applications. Here, we propose a novel solution which is expression of a promoterless miRNA-adapted shRNA (shmiRNA) from an engineered genomic miRNA locus. For proof-of-concept, we genetically “vaccinated” liver cells against a human pathogen, by using TALEns or CRISPR to integrate an anti-hepatitis C virus (HCV) shmiRNA into the liver-specific miR-122/hcr gene. Reporter assays and qRT-PCR confirmed anti-HCV shmiRNA expression as well as miR-122 integrity and functionality. Specificity and safety of shmiRNA integration were validated via PCR, cDNA and miRNA profiling, and whole genome sequencing. A subgenomic HCV replicon and a full-length reporter virus, but not a Dengue virus control, were significantly impaired in the modified cells. Our original combination of DNA engineering and RNA expression technologies should benefit numerous applications, from basic miRNA research, to human cell and gene therapy Four Huh7 cells lines at 3 different passages were analyzed. The reference cell line was Huh7 wild type cells (WT). The other three cell lines had an integration of an anti-HCV shmiRNA in the hcr locus and miR-122 intact (T2 31.3) or mutated (TS 30.20 and U6 20.16). RNA was extracted from three different passages.