Sulphur mustards inhibit binding of transcription factor AP2 in vitro

The bifunctional sulphur mustard (bis-(2-chloroethyl)sulphide, HD) and its monofunctional analogue (2-chloroethyl ethyl sulphide, CEES) are both vesicants. In this study, both mustards were shown to rapidly alkylate the AP2 consensus binding sequence incorporated in a 26mer oligonucleotide. The reaction was essentially complete within 10 min under the conditions employed in this study and -95% of the oligonucleotides were alkylated at least once using 500 microM HD and 1 mM CEES. Progressive alkylation of the consensus sequence was parallelled by a decrease in transcription factor binding. Under reaction conditions which alkylated approximately 95% of the oligonucleotides at least once, the binding of cloned human AP2 was reduced by 93 and 76% by HD and CEES, respectively, compared with control values. The interference with binding is a result of alkylation of the DNA and not damage to the transcription factor by mustard or its hydrolysis products. Interference with transcription factor binding would be expected to have a profound influence on the ability of the cell to function normally and to respond to DNA damage and may contribute significantly to the skin damage produced by these compounds.