Knowing when to let go

During meiosis I, some mechanism must allow homologous chromosomes to separate while keeping sister chromatids paired until meiosis II. How does a cell make this distinction? On page 219, Rogers et al. propose that in C. elegans the aurora-B kinase AIR-2 is largely responsible for ensuring that cohesion between chromosomes breaks down at the proper place and time. The authors also identified additional components in what is likely to be a conserved pathway controlling chromosome cohesion.

When AIR-2 activity is inhibited by RNAi, meiotic cells in the worm do not separate homologous chromosomes or sister chromatids. In metaphase I in normal meiotic cells, AIR-2 localizes distal to chiasmata, corresponding to the last points of contact between homologous chromosomes. In metaphase II, AIR-2 localizes to the last points of contact between sister chromatids. AIR-2 phosphorylates...