ENHANCEMENT OF AN MG2-DEPENDENT NUCLEASE ACTIVITY IN RAT-LIVER CELLS EXPOSED TO CISPLATIN()

An Mg2+-dependent deoxyribonuclease activity was highly purified from a 0.6 M NaCl extract of rat-liver nuclei. The template primer activity assay with a Klenow polymerase suggested that this nuclease plays a r ole in incision/excision of cisplatin-modified DNA strands to form sin gle-strand gaps. In another experiment, rat-liver (Ac2F) cells were cu ltured in the presence of cisplatin. A 0.6 M NaCl extract was prepared from the cultured-cell nuclei and subjected to the activity blotting analysis [Seki et al. (1993) J. Chromatography 618, 147-166]. The nucl ease activity of the extract was enhanced in response to cisplatin, bu t not in the presence of cycloheximide. These results imply that cispl atin-DNA lesions induce the Mg2+-dependent deoxyribonuclease activity in Ac2F cells to provide priming sites for the repair synthesis. (C) 1 994 Academic Press, Inc.