Figure 10.

Model for meiotic nuclear oscillation in fission yeast. (A) Astral microtubules are oriented with their minus ends (−) proximal to the SPB (a closed circle). The dynein-anchoring factors and microtubule-disassembling factors are located at the cortical regions around the cell ends and the anchoring factors on the cortical region proximal to the SPB are inactive. (B) Astral microtubules reach the polar cortical regions and cytoplasmic dynein (open circles) localized on the microtubule (a solid line) becomes anchored to the cortex by the anchoring factor. The anchored dynein generates a pulling force on the SPB by moving along the microtubule toward the minus end (small arrows) and promoting microtubule disassembly (dots). The pulling force drives nuclear migration toward the cortex (large arrows). (C) As the nucleus approaches the cortex, the microtubule is shortened and the active dynein-anchoring factors accumulate at the cortical region (dynein-anchoring factors on the left). (D) On arrival of the SPB at the microtubule interaction site, the microtubule becomes completely disassembled and the SPB pauses. The SPB inactivates the dynein anchoring factors localized at and around the cortical interaction site of the directing microtubule and releases dynein from the cortex. +, plus ends of microtubules; −, the minus ends of microtubules.