Figure 3. Changes in dCK substrate specificity and dCTP pool after IR.

(A) Western blot of purified 6-His-tagged dCK (WT or Ser⁷⁴ mutants) from 10K cells, and corresponding total cell lysates. (B) In vitro kinase assay on purified 6-His-tagged dCK (WT, S74A, S74E) using either [³H]-dC, [³H]-dG or [³H]-dA as a substrate before or after 3 Gy exposure (*, P = 0.0025; N = 2). (C) Intracellular dCTP pools before and hourly after 3 Gy exposure of 10K ± dCK (WT, S74A, S74E) cells (*, 10K vs. WT P = 0.0006; 10K vs. S74E P = 0.032; N = 6 for each time point).