Supplementary Figure 1: 8-oxodGTP inhibits telomerase activity.

(a) Telomerase reactions were conducted using (TTAGGG)₃ substrate (oligo #1 in Supplementary Table 1) and contained high dNTPs (lanes 1 - 4) or cellular dNTPs (lanes 5 - 8) and 0.3 μM ³²P-α-dGTP. Natural dGTP and 8-oxodGTP were mixed at 1:0, 1:1, and 0:1 ratios to maintain a total concentration of 500 μM or 5.2 μM of unlabeled guanine nucleotide. Lanes marked with 0* contained 0.3 μM ³²P-α-dGTP, and lacked unlabeled dGTP. Products were separated on polyacrylamide denaturing gels. The LC was a ³²P end-labeled 18-mer oligonucleotide. Numbers with plus sign indicate number of telomeric repeats added. (b) Products were quantitated and normalized to the LC, and used to calculate processivity (top graph) and relative activity (bottom graph). Bars represent the mean and s.d. from three independent reactions. Asterisks, ** p < 0.01, *** p < 0.001 based on two-tailed Student’s t test.