Fig. 6.

The catalytically inactive Top1Y723F-Clamp induces glr1Δ strain lethality. (A) Independent cultures of top1Δ or top1Δ, glr1Δ cells, transformed with the indicated YCpGAL1-top1 vector, were serially diluted 10-fold and spotted onto selective media supplemented with dextrose or galactose and 0.1μg/ml CPT as indicated. Cell viability was assessed after incubation at 30°C. (B) top1Δ or top1Δ, glr1Δ cells, transformed with the indicated YCpGAL1-top1 vector, were induced with galactose at t = 0. After 6 h, aliquots were plated on dextrose medium or processed for flow cytometry. The fold increases in the number of cells forming colonies, relative to t = 0, are an average of three independent experiments. In representative flow cytometry profiles, 1N and 2N DNA peaks are marked with single and double arrows, respectively.