Variants in the human double-stranded RNA (dsRNA) editing enzyme ADAR produce three well-characterized rare Mendelian Diseases: Dyschromatosis Symmetrica Hereditaria (DSH)(OMIM: 127400), Aicardi-Goutières syndrome (AGS)(OMIM: 615010) and Bilateral Striatal Necrosis/Dystonia (BSD). ADAR encodes p150 and p110 protein isoforms. p150 incorporates the Zα domain that binds left-handed Z-DNA and Z-RNA with high affinity through contact of highly conserved residues with the DNA and RNA double-helix. In certain individuals, frameshift variants on one parental chromosome in the second exon of ADAR produce haploinsufficiency of p150 while maintaining normal expression of p110. In other individuals, loss of p150 expression from one chromosome allows mapping of Zα p150 variants from the other parental chromosome directly to phenotype. The analysis reveals that loss of function Zα variants cause dysregulation of innate interferon responses to dsRNA. This approach confirms a biological role for the left-handed conformation in human disease, further validating the power of Mendelian genetics to provide unambiguous answers. The findings reveal that the human genome encodes genetic information using both shape and sequence.
The Zalpha domain of the editing enzyme dsRNA adenosine deaminase binds left-handed Z-RNA as well as Z-DNA
