FIGURE 6.

The yeast Top1-clamp⁴⁶⁰ induces a glr1Δ-dependent lethal phenotype. A, schematic representation of the domain structure of human and yeast Top1 (hTop1 and yTop1, respectively). Cysteine substitutions of conserved Gly and Ser residues (in boldface type) constitute the corresponding hTop1-clamp⁵³⁴ and yTop1-clamp⁴⁶⁰. B, congenic top1Δ yeast strains (GLR1 and glr1Δ), transformed with the indicated YCpGAL1-ytop1 constructs, were serially diluted and spotted onto SC-uracil plates supplemented with dextrose (Dex) or galactose (Gal), 25 mm HEPES, pH 7.2, Me₂SO and as indicated, CPT. As in Fig. 5, cell viability was assessed following incubation at 30 °C.