Cover: The transitional switch from A- to Z-conformation in a dsRNA substrate induces changes in site-selectivity and enzymatic activity of the RNA editing enzyme ADAR1 in vitro {see article by Koeris et al. in this issue [Nucleic Acids Res. (2006) 33, 5362–5370]}. A model of the ADAR1 Zα domain (bottom) is shown as a dimer bound to dsRNA in the Z-conformation (Placido et al., unpublished). DsRNA binding domains (dsRBDs) of ADAR1 bind dsRNA in the A-conformation with high affinity {shown on top is a dsRBD from Saccharomyces cerevisiae bound to a dsRNA hairpin. The atomic coordinates (PDB ID 1t4l) were obtained from the crystal structure of the complex published by Wu et al. [(2004) Proc. Natl Acad. Sci. USA]. The protein is shown with the α-helices red, the β-sheets cyan and the unstructured regions lime. The RNA purines are shown in blue while the pyrimidines are yellow. The image was created with the PyMol software (http://pymol.sourceforge.net/).
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