Abstract

Two DNA polymerases, A and B, isolated from cauliflower (Brassica oleracea, var. botrytis) were assayed for their deoxyribonuclease activities, using 3H-labeled DNA synthesized in vitro by cauliflower DNA polymerase-A. Nuclease activities were coeluted with the activities of DNA polymerase-A and -B by DNA-cellulose and phosphocellulose column chromatography and in the case of polymerase-B, this occurred even after treatment with subtilisin. Profiles of thermal inactivation, sensitivity to N-ethylmaleimide and inhibition by subtilisin of the nuclease activity resembled those of the polymerase activity in polymerase-B, but not those of polymerase-A. These observations suggest that at least DNA polymerase-B possesses an associated deoxyribonuclease activity. This nuclease exhibited a specificity for degradation of DNA in the 3′→5′ direction.

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