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. Author manuscript; available in PMC: 2012 Jan 1.
Published in final edited form as: Methods Cell Biol. 2011;103:115–147. doi: 10.1016/B978-0-12-385493-3.00006-1

Fig. 5. Kinetics of induction of phosphorylation of ATM on Ser1981, Chk2 on Thr68 and p53 on Ser15 in A549 cells treated with the DNA topoisomerase I inhibitor topotecan (Tpt).

Fig. 5

The bivariate distributions of DNA content versus, ATM-S1981P (top), Chk2-Thr68P (mid) and p53-S15P (bottom panels) of A549 cells treated with 150 nM Tpt for up to 6 h. Cells in G1, S and G2M can be identified based on differences in DNA content as marked in the control (time 0) culture. The dashed skewed lines represent the upper threshold level of IF for 97% of interphase (G1 and S) cells in the respective control cultures. The insets in the DNA versus ATM-S1981P distributions show DNA content frequency histograms of cells from time 0 (left) or 6 h Tpt treated (right) cultures. Note the accumulation of cells in early S-phase (arrow) as a result of cell arrest in S by Tpt after 6 h.