PerspectiveMolecular Biology

Directing the Centromere Guardian

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Science  08 Jan 2010:
Vol. 327, Issue 5962, pp. 150-151
DOI: 10.1126/science.1184770

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Accurate chromosome segregation during eukaryotic cell division requires the timely release of cohesion between duplicated chromosomes so that they may separate into two daughter cells. Errors in this process have been linked to cancer progression, infertility, and debilitating genetic diseases such as Down syndrome. A surveillance mechanism known as the spindle assembly checkpoint delays this release until all chromosome pairs are properly attached to a structure called the mitotic spindle. The enzyme Bub1 is essential for this checkpoint, but the targets of its phosphorylation activity have been elusive. On page 172 of this issue, Kawashima et al. (1) report that histone H2A—a protein associated with DNA within chromosomes—is a substrate of Bub1, and that H2A phosphorylation directs subsequent events that control chromatid cohesion and the checkpoint mechanism during the early stages of cell division.