Extracts from FLT3/ITD-expressing mouse BM MNCs showed decreased Ku86 and increased DNA Lig IIIα. Western blotting analysis of Ku86 in nuclear extracts (A) and DNA Lig IIIα and Ku70 in cell extracts (B) from BM MNCs of WT/ITD and WT/WT mice. Different amounts of cell extracts from a single homozygote ITD/ITD mouse were also examined. Lamin and actin are used as loading controls. (C) A schematic diagram of the DNA nick ligation assay. Annealing of 3 DNA oligonucleotides (15-, 19-, and 34-nt) gives rise to a substrate that contains a nick. DNA ligase I and IIIα in the cell extracts seal the nick. The 5′ end of the 15 mer was radiolabeled so that the product can be detected. (D) A phosphorimage showing the DNA nick ligation activity in cell extracts. The numbers at the bottom of lanes indicate the relative ligation activity. A vertical line has been inserted to indicate repositioned gel lanes.