Chromosomes can't let go

Like lovers reluctant to part, sister chromatids prolong their physical attachment during mitosis, according to Christoph Baumann, Erich Nigg (Max Planck Institute of Biochemistry, Martinsried, Germany), and colleagues. The researchers observed previously unreported chromatin threads that tether separating chromatids until late in anaphase. By monitoring tension in the forming threads during metaphase, a protein called PICH might help to ensure that microtubules are correctly attached to the kinetochores.

Nigg and colleagues chanced on the filaments while hunting for proteins under the control of Polo-like kinase 1. This kinase strips off the cohesins that bind chromosome arms together and performs a variety of other tasks during mitosis. The protein they discovered, PICH, is a predicted helicase that congregates on the kinetochores and centromeres. To the team's surprise, it also adorns enigmatic threads that connect sister chromatids...