Passenger proteins check in

Despite their name, the passenger proteins aren't just along for the ride during mitosis. They are busy helping control the attachment of spindle fibers to the chromosomes and ensuring that the cell splits after the chromosomes part.

But it was the proteins' seemingly bizarre movements that first caught the eye of William Earnshaw (now at the University of Edinburgh in the UK) and his colleagues in 1987. Previous work had demonstrated that sister chromatids can separate even when researchers cut the microtubules that form the spindle, suggesting that the centromere might house motors that propel the chromosomes. But cell biologists knew little about the centromere's architecture. In 1985, Earnshaw's lab snared the first three of the structure's components, which they dubbed the centromere proteins, or CENPs (Earnshaw and...