Molecular Pharmacology, Vol 4, 258-273, Copyright © 1968 by the American Society for Pharmacology and Experimental Therapeutics

The Effects of Nitrogen Mustard on DNA Template Activity in Purified DNA and RNA Polymerase Systems

¹ Department of Pharmacology, University of Michigan Medical School, Ann Arbor, Michigan 48104

The effects of nitrogen mustard (HN2) on DNA and RNA synthesis in preparations utilizing purified DNA templates and polymerase enzymes have been investigated in order to more completely define the mechanism of action of antineoplastic alkylating agents at the molecular level. Pretreatment of native calf thymus DNA with 5 x 10^-7 M HN2 produced a significant inhibition of DNA template activity in a purified RNA polymerase system from Escherichia coli. Concentrations of HN2 20-100 times higher were required to achieve an equivalent amount of inhibition of DNA template function utilizing a DNA polymerase system from E. coli. The template activities of both native and denatured DNA were inhibited by HN2. The quantity of alkylation of the DNA templates was determined by measuring the binding of ¹⁴C-HN2, and the percent inhibition of DNA template activity was correlated with the number of alkylations per 10⁴ nucleotide units. It was found that the template function of DNA as it exists in a nucleoprotein complex isolated from E. coli is relatively insensitive to treatment with HN2. The possible relationships of these findings to the cytotoxic effects of HN2 are discussed.

Note:
ACKNOWLEDGMENT The authors wish to thank Linda Galligher for her excellent technical assistance.