Figure 2.

Arsenic-induced alterations in global DNA methylation. Global DNA methylation as determined in genomic DNA isolated from control and arsenic-transformed cells. (A) Isolated DNA digested with MspI (left lane of each numbered group) and its methyl-sensitive isoschizomer HpaII (right lane of each numbered group), followed by Southern blot analysis using rat satellite I DNA repeat fragment probe pCR-J00784. Groups: 1, control cells at 18 weeks; 2 and 3, duplicates of cells acutely treated with 1.0 μM arsenic; 4–6, triplicates of arsenic-transformed cells with 0.5 μM arsenic for 18 weeks. (B) Densitometric analysis of the results of the Southern blots from control and chronic (18 weeks) or acute (48 hr) arsenic exposure at the concentrations indicated. Data represent mean ± SEM of triplicate experiments.