Polymerase-chain reaction as a tool for investigations on sequence-selectivity of DNA-drugs interactions.

Sequence-selectivity of DNA-binding drugs was recently reported in a number of studies employing footprinting and gel retardation approaches. In this paper we performed polymerase-chain reaction (PCR) experiments to study the in vitro effects of distamycin, daunomycin, chromomycin and mithramycin. As model systems we employed the human estrogen receptor (ER) gene and the Harvey-ras (Ha-ras) oncogene, in order to obtain PCR products significantly differing for the A + T/G + C frequency ratio. Distamycin, daunomycin, chromomycin and mithramycin are indeed known to differentially bind to different DNA regions depending upon the DNA sequences recognized. The main conclusion of our experiments is that distamycin, daunomycin, chromomycin and mithramycin inhibit polymerase-chain reaction in a sequence-dependent manner. Distamycin inhibits indeed PCR mediated amplification of AT-rich regions of the human estrogen receptor gene, displaying no inhibitory effects on PCR-mediated amplification of GC-rich sequences of Ha-ras oncogene. By contrast daunomycin, chromomycin and mithramycin were found to inhibit PCR-mediated amplification of the Ha-ras GC-rich oncogene sequences. We propose that polymerase-chain reaction technique could be applied to study the in vivo interactions of DNA-binding drugs to specific genes in intact cells.