Figure 4.

Requirement of Mid1p for actomyosin ring maintenance in metaphase in the absence of functional Cdc15p. (A) mid1-18 pREP1-mad2⁺ rlc1-GFP and cdc15-140 mid1-18 pREP1-mad2⁺ rlc1-GFP cells were arrested in metaphase by growth in medium lacking thiamine for 24 h. Cells were shifted to the restrictive temperature for 3 h or kept at the permissive temperature as control, fixed and stained with α-GFP antibodies, α-TAT1 antibodies, and DAPI to visualize actomyosin rings, tubulin, and DNA, respectively. (B) Quantitation of actomyosin rings in cells with short (metaphase) spindles in mid1-18 pREP1-mad2⁺ rlc1-GFP at the restrictive temperature (■) and cdc15-140 mid1-18 pREP1-mad2⁺ rlc1-GFP at the restrictive (□; y = 0) and permissive temperature (▩).