Binding of cisplatin to specific sequences of human DNA in vitro

Cisplatin was reacted with a 184-base-pair sequence, exon 3, of human HPRT DNA in vitro. The binding sites were mapped by a primer extension method with T4 DNA polymerase and radioactive dCTP. Binding sites of cisplatin were indicated by the lengths of synthesized polynucleotides as determined by gel electrophoresis. Neighboring GG dinucleotides were highly preferred sites of binding by cisplatin, while less binding was noted to GXG, GA, AAA, and GXA. Analysis by densitometry revealed a 5-fold difference in binding among the GG sequences. The relative binding to a GGG sequence exceeded that of a GGGGGG sequence, suggesting that the number of Gs in a run did not determine the relative binding.