Sequence specificity and reactivity of the binding of phenazine-tethered platinum complexes to DNA.

An in vitro transcription assay was used to probe the sequence specificity of the binding of phenazine-tethered platinum complexes to DNA. It was found that when compared to cis-dichloro(ethylenediamine)platinum(II), the number of RNA polymerase blockage sites was increased by approximately 50% and the blockage sites were broadened by 1-3 nucleotides by the presence of the phenazine ligand. The rate of platination was also enhanced by the presence of the intercalator, and the increase in the kinetics of platination resulted in increased levels of adducts formed (i.e. high drug occupancy) as detected under conditions of active transcription. The level of platination by derivative 3 was 20-fold greater than that of the reference compound, which lacked a tethered intercalating phenazine group.