Adoption of A-Z Junctions in RNAs by Binding of Zα Domains

Abstract

While DNA and RNA helices often adopt the canonical B- or A-conformation, the fluid conformational landscape of nucleic acids allows for many higher energy states to be sampled. One such state is the Z-conformation of nucleic acids, which is unique in that it is left-handed and has a "zigzag" backbone. The Z-conformation is recognized and stabilized by Z-DNA/RNA binding domains called Zα domains. We recently demonstrated that a wide range of RNAs can adopt partial Z-conformations termed "A-Z junctions" upon binding to Zα and that the formation of such conformations may be dependent upon both sequence and context. In this chapter, we present general protocols for characterizing the binding of Zα domains to A-Z junction-forming RNAs for the purpose of determining the affinity and stoichiometry of interactions as well as the extent and location of Z-RNA formation.

Keywords: Analytical ultracentrifugation; A–Z junctions; Circular dichroism; Ez score; Isothermal titration calorimetry; Nuclear magnetic resonance; Z-RNA; Zα domains.