A 6 bp Z‐DNA hairpin binds two Zα domains from the human RNA editing enzyme ADAR1

Abstract The Zα domain of the human RNA editing enzyme double-stranded RNA deaminase I (ADAR1) binds to left-handed Z-DNA with high affinity. We found by analytical ultracentrifugation and CD spectroscopy that two Zα domains bind to one d(CG) 3 T 4 (CG) 3 hairpin which contains a stem of six base pairs in the Z-DNA conformation. Both wild-type Zα and a C125S mutant show a mean dissociation constant of 30 nM as measured by surface plasmon resonance and analytical ultracentrifugation. Our data suggest that short (≥6 bp) segments of Z-DNA within a gene are able to recruit two ADAR1 enzymes to that particular site.