Metazoan-like kinetochore arrangement masked by the interphase RabI configuration

Abstract

During cell cycle progression in metazoan, the kinetochore, the protein complex attached to centromeres which directly interacts with the spindle microtubules, the vehicle of chromosome segregation, is assembled at mitotic onset and disassembled during mitotic exit. This program is assumed to be absent in budding and fission yeast because kinetochore proteins are stably maintained at the centromeres throughout the entire cell cycle. In this work, we show that the assembly program at the mitotic onset of the Ndc80 complex, a crucial part of the outer kinetochore, is unexpectedly conserved in Schizosaccharomyces pombe. We have identified this behavior by removing the Rabl chromosome configuration during interphase, in which centromeres are permanently associated with the nuclear envelope beneath the spindle pole body. Hence, the Rabl configuration masks the presence of a program to recruit Ndc80 at mitotic onset in fission yeast, similar to that taking place in metazoan. Besides the evolutionary implications of our observations, we think that our work will help understand the molecular processes behind the kinetochore assembly program during mitotic entry using fission yeast as the model organism.