Chromatid cohesion during mitosis: lessons from meiosis

The equal distribution of chromosomes during mitosis and meiosis is depende nt on the maintenance of sister chromatid cohesion. In this commentary we r eview the evidence that, during meiosis, the mechanism underlying the cohes ion of chromatids along their arms is different from that responsible for c ohesion in the centromere region. We then argue that the chromatids on a mi totic chromosome are also tethered along their arms and in the centromere b y different mechanisms, and that the action of these two mechanisms can be temporally separated under various conditions. Finally, we demonstrate that in the absence of a centromeric tether, arm cohesion is sufficient to main tain chromatid cohesion during prometaphase of mitosis. This finding provid es a straightforward explanation for why mutants in proteins responsible fo r centromeric cohesion in Drosophila (e.g. ord, mei-s332) disrupt meiosis b ut not mitosis.