APC-Mediated Proteolysis of Ase1 and the Morphogenesis of the Mitotic Spindle

Abstract

The molecular mechanisms that link cell-cycle controls to the mitotic apparatus are poorly understood. A component of the Saccharomyces cerevisiae spindle, Ase1, was observed to undergo cell cycle-specific degradation mediated by the cyclosome, or anaphase promoting complex (APC). Ase1 was degraded when cells exited from mitosis and entered G ₁ . Inappropriate expression of stable Ase1 during G ₁ produced a spindle defect that is sensed by the spindle assembly checkpoint. In addition, loss of ASE1 function destabilized telophase spindles, and expression of a nondegradable Ase1 mutant delayed spindle disassembly. APC-mediated proteolysis therefore appears to regulate both spindle assembly and disassembly.