Figure 5.

Influence of knockdown of the DNA repair protein PNKP on low-dose radiation response as measured by (a) clonogenic survival, (b) ATM phosphorylation and (c) H2AX phosphorylation. All data points are based on three independent determinations. Error bars indicate SEM. Clonogenic survival indicates no IRR in the PNKP-deficient cell line (A549δPNKP). Measuring γH2AX in these cells also shows that limited dephosphorylation, i.e. repair, is occurring. ATM phosphorylation, however, occurs in a similar fashion to that observed in the parental cell line.