Figure 5. Compound 15 causes nuclear DNA damage in vivo.

A. DNA repair mutants are sensitive to compound 15. Ten-fold serial dilutions of the indicated deletion mutant strains were spotted on media containing 1% DMSO, 0.7 µM compound 13 (0.08 EC₅₀), or 4.5 µM compound 15 (0.08 EC₅₀). Mutants in nucleotide excision repair (NER), postreplication repair (PRR), and homologous recombination repair (HR) are indicated. B. Compound 15 activates the DNA damage checkpoint kinase Rad53. Asynchronous populations of cells (asyn), or cells arrested in G1 (αF) or G2/M (noc), were treated with 56 µM compound 15, or with 0.035% MMS, for 2 hours. Following TCA fixation, cell extracts were fractionated on SDS-PAGE and Rad53 was detected by immunoblot analysis. The effect of the vehicle DMSO (D) is also shown. C. Compound 15 induces mutagenesis. Cells were treated with vehicle (DMSO), 0.035% MMS, 9 µM compound 13, or 56 µM compound 15 for 2 hours. The average mutation rate is plotted, with error bars spanning one standard deviation.