Alkaline Endonuclease(s) Activity in the Thymus and Spleen of Normal and Irradiated Mice

Abstract

An alkaline endonuclease activity in the cytoplasmic and nuclear fraction isolated from the thymus and spleen of mice was found. Chromatin-associated endonuclease activity was identified only in the spleen. The enzyme(s) was active on single- and double-stranded DNA, but the reaction was faster if single-stranded DNA was used as a substrate. Maximum activity was found in the pH range of 7.9-8.1 in the presence of 10 mM Mg2+ and 1 mM Ca2+. The enzyme(s) splits DNA, yielding 3''-hydroxyl terminated polynucleotides. This alkaline endonuclease(s) may be responsible for formation of deoxyribopolynucleotides in the thymus and spleen of irradiated mice.