Detecting Z-RNA and Z-DNA in Mammalian Cells

Eukaryotic cells sense and respond to virus infections by detecting conserved virus-generated molecular structures, called pathogen-associated molecular patterns (PAMPs). PAMPs are usually produced by replicating viruses, but not typically seen in uninfected cells. Double-stranded RNA (dsRNA) is a common PAMP produced by most, if not all, RNA viruses, as well as by many DNA viruses. DsRNA can adopt either the right-handed (A-RNA) or the left-handed (Z-RNA) double-helical conformation. A-RNA is sensed by cytosolic pattern recognition receptors (PRRs) such as RIG-1-like receptor MDA-5 and the dsRNA-dependent protein kinase PKR. Z-RNA is detected by Zα domain containing PRRs, including Z-form nucleic acid binding protein 1 (ZBP1) and the p150 subunit of adenosine deaminase RNA specific 1 (ADAR1). We have recently shown that Z-RNA is generated during orthomyxovirus (e.g., influenza A virus) infections and serves as activating ligand for ZBP1. In this chapter, we describe our procedure for detecting Z-RNA in influenza A virus (IAV)-infected cells. We also outline how this procedure can be used to detect Z-RNA produced during vaccinia virus infection, as well as Z-DNA induced by a small-molecule DNA intercalator.