A single lentiviral vector platform for microRNA-based conditional RNA interference and coordinated transgene expression

RNAi is proving to be a powerful experimental tool for the functional annotation of mammalian genomes. The full potential of this technology will be realized through development of approaches permitting regulated manipulation of endogenous gene expression with coordinated reexpression of exogenous transgenes. We describe the development of a lentiviral vector platform, pSLIK (single lentivector for inducible knockdown), which permits tetracycline-regulated expression of microRNA-like short hairpin RNAs from a single viral infection of any nalive cell system. In mouse embryonic fibroblasts, the pSLIK platform was used to conditionally deplete the expression of the heterotrimeric G proteins G alpha 12 and G alpha 13 both singly and in combination, demonstrating the Ga13 dependence of serum response element-mediated transcription. In RAW264.7 macrophages, regulated knockdown of G beta 2 correlated with a reduced Ca2+ response to C5a. Insertion of a GFP transgene upstream of the G beta 2 microRNA-like short hairpin RNA allowed concomitant reexpression of a heterologous mRNA during tetracycline-dependent target gene knockdown, significantly enhancing the experimental applicability of the pSLIK system.