Inhibition of Mad2 (purple dots), but not Bub3 (red line), hastens anaphase in the absence of spindle attachment problems.

Sorger/Elsevier

Two spindle checkpoint proteins work away from the kinetochore to regulate mitotic timing, based on work from Patrick Meraldi, Viji Draviam, and Peter Sorger (MIT, Cambridge, MA). This control may kick in even before a kinetochore is assembled.

The mitotic checkpoint—controlled by Mad1, Mad2, Bub1, BubR1, and Bub3— delays anaphase by inhibiting APC until all kinetochores are properly attached to the spindle. Because inhibition of Mad2 leads to an accelerated mitosis and a precocious anaphase, it has been assumed that the checkpoint itself also regulates mitotic timing.

But Mad2 does not represent all of its kinetochore partners. “The assumption was that all were required for the checkpoint, so all would be needed here too,” says Meraldi. But the authors found that only Mad2 and BubR1...

The Rockefeller University Press
2004
The Rockefeller University Press
2004
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