RNaseH2 mutants that cause Aicardi–Goutieres syndrome are active nucleases

Abstract

Mutations in the genes encoding the RNaseH2 and TREX1 nucleases have been identified in patients with Aicardi–Goutieres syndrome (AGS). To determine if the AGS RNaseH2 mutations result in the loss of nuclease activity, the human wild-type RNaseH2 and four mutant complexes that constitute the majority of mutations identified in AGS patients have been prepared and tested for ribonuclease H activity. The heterotrimeric structures of the mutant RNaseH2 complexes are intact. Furthermore, the ribonuclease H activities of the mutant complexes are indistinguishable from the wild-type enzyme with the exception of the RNaseH2 subunit A (Gly37Ser) mutant, which exhibits some evidence of altered nuclease specificity. These data indicate that the mechanism of RNaseH2 dysfunction in AGS cannot be simply explained by loss of ribonuclease H activity and points to a more complex mechanism perhaps mediated through altered interactions with as yet identified nucleic acids or protein partners.