Fission yeast Skp1 is required for spindle morphology and nuclear membrane segregation at anaphase

Skp1 is a core component of the Skp1-Cullin-1-F-box ubiquitin ligase. Here, we show a novel role for fission yeast Skp1 in mitotic progression. Temperature-sensitive skp1-A7 mutants enter mitosis, but fail to execute anaphase. Time-lapse imaging shows that spindles in this mutant form intranuclear arch-like structures, which eventually collapse abruptly. The two spindle poles are also seen to move backward to the cell centre rather than towards the cell ends. These abnormal phenotypes appear to stem from defects in nuclear membrane segregation. Our results show that Skp1 is required for coordinated structural alterations of mitotic spindles and nuclear membranes.