DNA Polymerases in Normal and Leukemic Human Hematopoietic Cells

Abstract

Abstract DNA polymerase activities were assayed in bone marrow cells and peripheral leukocytes from normal people and patients with acute myelogenous, chronic lymphocytic, and chronic myelogenous leukemia. Extracts of subcellular components were fractionated by velocity sedimentation through sucrose density gradients and assayed using activated DNA as template. Two major DNA-dependent DNA polymerases were found in human cells with molecular weights of approximately 50,000 and 200,000 daltons, respectively. The DNA polymerase of high molecular weight is located in the soluble cytoplasmic fraction and is inhibited by N-ethylmaleimide. The low molecular weight polymerase is detected in extracts of nuclei and in the soluble fraction. It is resistant to inhibition by N-ethylmaleimide. In all cell types tested, total DNA polymerase activities were much higher in cytoplasmic than in nuclear extracts. Lymphocytes purified from normal peripheral blood had three to four times as much of both the high and low molecular weight polymerase activities per cell as purified granulocytes. Leukemic myeloblasts had 10 to 20 times as much cytoplasmic DNA polymerase activity as more mature leukocytes from normal peripheral blood. In general, immature granulopoietic cells contained higher total DNA polymerase activities than more mature granulocytes, and the major increases in polymerase activities were in the high and low molecular weight cytoplasmic enzymes rather than in the nuclear enzyme.