Sensitivity of parental (W303-1B), rad52, yku70, and yku70 rad52 strains to HN2 and the monofunctional mustard HN1. (A) Exponential-phase cells were treated with 0 to 1,000 μM HN2. (B) Stationary-phase cells were treated with 0 to 1,000 μM HN2. (C) Exponential-phase cells were treated with doses from 0 to 10,000 μM HN1. All results are the means of at least three independent experiments, and the vertical error bars show the standard error of the mean.