Figure 1.

S. pombe mad2p functions as a spindle-assembly checkpoint protein. (A) Open reading frame of S. pombe mad2 (GenBank accession no. U72150) aligned with the S. cerevisiae Mad2p (GenBank accession no. U14132). Identical amino acids are labeled with stars and conserved amino acids are labeled with dots. (B) Hypersensitivity of mad2^Δ to thiabendazole (TBZ) treatment. Serial dilutions (1/5) of an equal number of mad2^Δ and wild-type cells were spotted on Edinburgh minimum medium plates with the indicated concentration of TBZ. (C) Viability test of the single mutants mad2^Δ and nda3–311^cs and the double mutant mad2^Δ nda3–311^cs after a transient incubation at 18°C. Colonies on each plate were counted and the percentage of viable cells was calculated by normalization to the colony number of the 0-hr samples. (D) Flow-cytometric analysis of DNA content of the single mutants mad2^Δ and nda3–311^cs and the double mutant mad2^Δ nda3–311^cs after a transient incubation at 20°C. The relative fluorescence corresponding to 2C and 4C DNA content is marked by arrows; hours indicate the length of 20°C incubation.