Figure 4: TRF1 suppresses UVC-induced CPD and 6–4PPs formation in telomeric fragments.

(a) Purified duplex DNA restriction fragments (25 μg ml−1) containing (TTAGGG)270 repeats (1.6 kb, telomeric) or non-telomeric sequence (1.5 kb, genomic) were exposed to 100 J m−2 UVC. Before irradiation fragments were preincubated for 45 min at room temperature with either no protein (−), 2 μM TRF1, or 2 μM BSA. Various amounts of fragments from each reaction were immunoblotted for CPDs (a) or 6–4PPs (b). The antibody signal intensities were quantitated, and amounts within the linear range (3 ng for CPD and 7 ng for 6–4PP) were normalized to the no protein controls, and plotted for each condition. Values and error bars are the mean and s.d. from three independent experiments. The differences between telomeric DNA+TRF1 versus telomeric DNA+BSA and telomeric DNA+TRF1 versus genomic DNA+TRF1 were statistically significant by one-way ANOVA; P-values indicated in the figure.