Figure 3.

DNA from mouse ES cells containing disrupted Msh2 genes accumulates more oxidative base damage as a consequence of low-level radiation exposure than wt ES cells. (A) Increases in oxidized dGua (8OHdGua) in DNA from different ES cell lines treated with low-level radiation, assessed by using HPLC-ECD (see Materials and Methods), are displayed as a ratio of the number of detected 8OHdGua per 10⁶ dGua in irradiated vs. unirradiated cell cultures. (B) Levels of the oxidized bases 8-hydroxyadenine (8OHAde) and thymine glycol (TG) as well as levels of 5-methylcytosine (5-MeCyt) in DNA from ES cells with and without defective mismatch repair (i.e., Msh2^+/+ and Msh2^−/−, respectively) were determined before and after low-level irradiation by GC/MS-SIM (see Materials and Methods). For both HPLC-ECD and GC/MS-SIM, DNA from ES cells was collected and pooled following at least five independent exposures before being subjected to analysis for oxidized bases.