Figure 4.

Time dependence of formation of mitoxantrone–DNA adducts. (A) DNA (90 µM bp) was incubated with 20 µM mitoxantrone and 6 mM formaldehyde for 0–30 min at 37°C. Reactions were terminated by ethanol precipitation prior to transcription initiation with subsequent elongation for 5 min. C1 and C2 are controls lacking mitoxantrone and formaldehyde, respectively. (B) The mole fraction of transcriptional block 4 (44mer) is plotted as a percentage of all transcripts in the lane and expressed as a function of drug–DNA reaction time. (C) Loss of full-length transcript (A) with incubation time.