The interaction of cisplatin with a human telomeric DNA sequence containing seventeen tandem repeats

The anti-tumour drug, cisplatin, preferentially forms adducts at G-rich DNA sequences. Telomeres are found at the ends of chromosomes and, in humans, contain the repeated DNA sequence (GGGTTA)n that is expected to be targeted by cisplatin. Using a plasmid clone with 17 tandem telomeric repeats, (GGGTTA)17, the DNA sequence specificity of cisplatin was investigated utilising the linear amplification procedure that pin-pointed the precise sites of cisplatin adduct formation. This procedure used a fluorescently labelled primer and capillary electrophoresis with laser-induced fluorescence detection to determine the DNA sequence specificity of cisplatin. This technique provided a very accurate analysis of cisplatin-DNA adduct formation in a long telomeric repeat DNA sequence. The DNA sequence specificity of cisplatin in a long telomeric tandem repeat has not been previously reported. The results indicated that the 3′-end of the G-rich strand of the telomeric repeat was preferentially damaged by cisplatin and this suggests that the telomeric DNA repeat has an unusual conformation.