Ribonuclease H. An Enzyme Degrading the RNA Moiety of DNA-RNA Hybrids

Abstract

Extracts from calf thymus contain an enzyme degrading the RNA moiety of DNA-RNA hybrids. An assay for this enzyme and several characteristics of the enzyme reaction are described. The specificity of the enzyme for DNA-RNA hybrids is indicated by several lines of evidence: The RNA of the hybrid is rendered resistant to the action of this enzyme upon heating. Nucleic acids other than DNA-RNA hybrids are not affected to a comparable degree. The enzyme rapidly degrades polyribouridylic acid if it is hybridized to polydeoxyriboadenylic acid, but not if it is hybridized to polyriboadenylic acid. Experiments with double labelled DNA-RNA hybrids show that specifically the RNA moiety of the hybrid and not the DNA is attacked by the enzyme.