Nuclear Translocation of DNase II and Acid Phosphatase during Radiation-induced Apoptosis in HL60 Cells

Abstract

DNase II is involved in DNA fragmentation induced by a variety of treatments. However, according to past reports DNase II does not directly generate TUNEL (in situ DNA end labeling)-positive cells. The purpose of this study was to investigate the participation of acid phosphatase in the generation of TUNEL-positive cells. DNase II-like proteins, whose molecular weights were 32-kDa, were detected in nuclear extracts of HL60 human myeloid leukemia cells post γ-irradiation by SDS-PAGE and immunohistochemistry. Acidic nuclease activity was especially active in 32-kDa bands. TUNEL assay was positive post γ-irradiation. From measurements of the activity of acid phosphatase, the activity in nuclear extracts increased remarkably post γ-irradiation. γ-irradiation can directly or indirectly activate DNase II. Once DNase II and acid phosphatase have been translocated from lysosomes into the nuclei, DNase II generates TUNEL reactive ends in combination with acid phosphatase.