Fig. 3.

Chromosome segregation in fly and vertebrate mitosis. In prophase chromosomes, the cohesin complexes are located along the middle region of the arms and at the inner centromere domain. During the prophase/metaphase transition, the kinases Aurora-B and/or Polo-like kinase 1 (PLK1) phosphorylate the SA2 subunit of most cohesin complexes at the arms and promote their removal from chromosomes. Wing apart-like (WAPL) is a regulator of sister chromatid resolution in the mitotic prophase. Centromere cohesins are protected from phosphorylation by phosphatase PP2A, which is recruited to the centromere by shugoshin. Once all chromosomes are bi-oriented at the metaphase plate in the metaphase/anaphase transition, shugoshin and PP2A are delocalized from the centromeres. At this time, the APC/CDC20 complex ubiquitinizes the separase inhibitor securin, which is dissociated from separase, allowing cleavage of the few remaining cohesin complexes at the arms and centromere cohesins