Just two peaks of tubulin (white), at spindle pole bodies, reveal that no microtubule overlap is found during mating.
After two yeast cells fuse, their genomes come together via oppositely oriented microtubule sets whose plus ends face each other at the fusion site. The old model of this DNA congression suggested that the Kar3p microtubule minus end–directed motor pulled the plus end of one microtubule toward the minus end of its counterpart. Upon reaching the spindle pole body, Kar3p was thought to depolymerize the microtubule minus ends.
Recent findings put doubt on this 15-yr-old model. For one, minus end–directed motors generally accumulate on plus ends. Kar3p was indeed shown in vitro to depolymerize plus ends, where most microtubule dynamics is...
