Fig. 4. Abundance of DNA repair proteins Ku80, Ku70 and RPA70 in chromatin-enriched fractions, following exposure of Ku80^+/- cells to mimosine or hydroxyurea. Chromatin fractions were prepared from HCT116 and Ku80^+/- cells that were either untreated or treated with thymidine/mimosine or thymidine/hydroxyurea double block. (A) Ten and 20 µg were subjected to electrophoresis and transferred onto PVDF membrane. They were then immunoblotted with 1/1000^th dilution of anti-Ku80 (H300), 1/1000^th dilution of anti-Ku70 (C-19), anti-RPA70, or anti-actin. (B) Quantification of the immunoblots after normalization for actin. Averages of three experiments and 1 s.d. are shown.