The effect of DNA-alkylating agents on gene expression from two integrated reporter genes in a mouse mammary tumor line

A model system was developed to investigate the effects of DNA alkylating agents on cellular gene expression. The cytomegalovirus immediate-early promoter (CMV) and the mouse mammary tumor virus promoter (MMTV) were coupled separately to the luciferase reporter gene and stably expressed in cultured cells. The change in luciferase activity was used as a measure of gene expression inhibition. Seven well-characterized DNA alkylating agents of varied DNA adduct-forming ability were evaluated in this system. The major groove binders/intercalators (that form guanine adducts) increased CMV–luciferase activity above background, while minor groove binders (that form adenine adducts) all decreased it. The MMTV–luciferase activity was remarkably different to the CMV–luciferase activity and was inhibited to the greatest extent by the minor groove alkylators. One of these, a polybenzamide with spatially separated alkylating groups, inhibited gene expression to a greater extent than inhibition of general DNA or RNA synthesis.