DNA damage foci in wild-type and <i>Nth1^−/−</i> primary MEFs.

<p>53BP1 foci at genome or telomeres are detected by IF and IF-telomere FISH, respectively. (A) Percentage of wild-type and <i>Nth1^−/−</i> cells with various numbers of 53BP1 foci in the genome. (B) Percentage of wild-type and <i>Nth1^−/−</i> cells with greater than or equal to three 53BP1 foci that colocalize with telomere DNA. APH: cells treated with 0.2 uM aphidicolin for 16 hours. (C) A representative <i>Nth1^−/−</i> cell showing telomeric DNA (red) and 53BP1 foci (green). N = 4 mice, at least 100 cells/sample are counted. Error bars indicate standard deviation. P-values are calculated using a Student's <i>t</i>-test and adjusted using Benjamini-Hochberg False Discovery Rate -controlling method. P-values<0.05 are statistically significant using the above method.