Characterization of Different Deoxyribonucleases in Human Lymphocytes

Four groups of deoxyribonuclease activities from human lymphocytes have been characterized by deoxyribonuclease assay in DNA-containing polyacrylamide gels following their separation by disc-electrophoresis. All activities hydrolyse DNA endonucleolytically. One neutral deoxyribonuclease found in the cytoplasmic fraction prefers native or UV-irradiated DNA over denatured DNA as substrate and is a 5'-monoester former. Two groups of acid deoxyribonuclease activities are detectable in the nuclear fraction. Both are 3'-monoester formers. One is as well active with denatured DNA as with native DNA, the other one shows the same activity with native and UV-irradiated DNA but lower activity with denatured DNA. An alkaline deoxyribonuclease activity, also localized in the nucleus, is a 5'-monoester former, and prefers denatured or UV-irradiated DNA as substrate.