Specific inhibition of DNA polymerase-associated RNase H by DNA

Abstract

The RNase H activity associated with several RNA-directed DNA polymerases is inhibited by the addition of DNA, unlike to RNase H activity from enzymes devoid of polymerizing activity. Kinetic investigations of the inhibitory effect of DNA, using purified Rauscher leukemia virus DNA polymerase as a test enzyme, revealed that the addition of DNA to an ongoing RNase H reaction causes an immediate cessation of RNase H activity. Concomitant initiation of DNA synthesis directed by inhibitory DNA can occur, provided that appropriate substrate and primer is available. Thus, besides providing a simple test for the distinction between polymerase-associated and polymerase-independent RNase H activity, this study strongly indicates that RNase H activity expressed by several mammalian oncoviral reverse transcriptases [from avian myeloblastosis virus and simian sarcoma virus] is an integral part of that molecule, and that the catalytic site of RNase H activity is also involved in template-primer binding.