Meiosis II spindle disassembly requires two distinct pathways

Abstract

During exit from meiosis II, cells undergo several structural rearrangements, including disassembly of the meiosis II spindles and cytokinesis. Each of these changes is regulated to ensure that they occur at the proper time. Previous studies have demonstrated that both SPS1, which encodes a STE20-family GCKIII kinase, and AMA1, which encodes a meiosis-specific activator of the Anaphase Promoting Complex, are required for both meiosis II spindle disassembly and cytokinesis in the budding yeast Saccharomyces cerevisiae. We examine the relationship between meiosis II spindle disassembly and cytokinesis and find that the meiosis II spindle disassembly failure in sps1Δ and ama1∆ cells is not the cause of the cytokinesis defect. We also see that the spindle disassembly defects in sps1Δ and ama1∆ cells are phenotypically distinct. We examined known microtubule-associated proteins Ase1, Cin8, and Bim1, and found that AMA1 is required for the proper loss of Ase1 and Cin8 on meiosis II spindles while SPS1 is required for Bim1 loss in meiosis II. Taken together, these data indicate that SPS1 and AMA1 promote distinct aspects of meiosis II spindle disassembly, and that both pathways are required for the successful completion of meiosis.

Abstract

• Cells disassemble the meiotic spindle as they exit meiosis. In S. cerevisiae, meiotic exit is regulated by two parallel pathways using meiosis-specific factors: Sps1 (a STE20-GCKIII kinase) and Ama1 (a meiotic regulator of the APC/C).

• The authors find that SPS1 and AMA1 regulate distinct processes during meiotic spindle disassembly. AMA1 is needed to remove Ase1 and Cin8 while SPS1 is needed for the removal of Bim1.

• Thus, although the regulatory molecules governing exit from meiosis differ from mitosis, the overall regulatory architecture is similar. In mitosis, APC/C ^Cdh1 regulates Ase1 and Cin8 while the Dbf2/Mob1 Mitotic Exit Network regulates Bim1.