The spindle assembly checkpoint

The spindle assembly checkpoint (SAC) is a signal transduction machinery that monitors the correct attachment of chromosomes to spindle microtubules during cell division and arrests cell cycle progression if the attachments are faulty. The action of the SAC is therefore crucial in the prevention of chromosome mis-segregation and aneuploidy. Although much progress has been made recently in understanding how the SAC works, many key questions remain unanswered. In particular, it is unclear how the SAC signal is dynamically integrated with microtubule-kinetochore attachment to ensure prompt silencing of the SAC once all chromosomes are correctly attached. We have recently identified the PP2A-B56 form of PP2A as a key regulator of spindle checkpoint signalling (Espert et al., 2014). Our current research is focused on understanding the precise contributions and relative importance of PP1 and PP2A-B56 to the control of SAC signal transduction, as well as the temporal order in which these two phosphatases act.