The nature of DNA breakage by 4'-[(9-acridinyl)amino]methane-sulphon- m-anisidide

Abstract

Auhough recent studies have shown that the anticancer drug 4’-[(9-acridinyl)amino]methanesulphon-m-anisidide (mAMSA) induces doublestrand breaks in the DNA of treated cells [1,2] the exact sites or nature of these breaks in DNA are unknown. Zwelling et al. [l] have concluded that the DNA isolated from mAMSA-treated cells is associated with protein because it binds to polyvinyl chloride filters during the alkaline-elution procedure [3] and they have suggested that intercalation of mAMSA into cellular DNA may break the DNA by inducing topoisomerase action leading to the association of DNA fragments with topoisomerase. A similar suggestion has been made regarding other intercalating drugs [4]. In view of these suggestions it is of considerable interest to determine whether the termini of DNA fragments produced following mAMSA action are in fact associated with proteins in the manner expected if topoisomerases sever the DNA. To examine this question we have used phage T4 polynucleotide kinase to assess the availability of 5’-termini on DNA fragments produced after treating PY815 mouse mastocytoma cells in culture with mAMSA. Our results indicate that the DNA 5’-termini are not available for phosphorylation consistent with the view that they may be linked to protein. was from Calbiochem. Snake venom phosphodiesterase, ribonuclease Tl and pancreatic ribonuclease were from Worthington Biochemical Corp. Calf intestinal alkaline phosphatase was from Sigma Corp., Phage X DNA was obtained from Miles Laboratories and Proteinase K from Boehringer. [$*P]ATP (spec. act. 5700 Ci/mmol) was from Amersham, U.K.