Figure 6: A cyclobutane pyrimidine dimer inhibits TRF1 binding to telomeric DNA.

The TRF1 homodimer binding sequence and site specific CPD (⁁) is shown. (a) Substrates (2.5 nM) consisting of annealed Ctrl/TPL or CPD/TPL duplexes were incubated with decreasing TRF1 concentrations (200, 100, 50 or 25 nM) for 20 min in binding buffer, and reactions were run on a 5% acrylamide native gel. Bound and unbound (free) substrate are indicated. (b) The per cent bound was calculated and plotted against TRF1 concentration. Circle and dotted line, control (Ctrl); square and solid line CPD-containing substrate (CPD). Values and error bars indicate the mean and s.d. from three independent experiments. The difference between the curves was statistically significant; P=4.0 × 10⁻¹¹ by two-way analysis of variance.