Spindle assembly checkpoint

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Spindle assembly checkpoint (SAC), or named as spindle checkpoint, is a vital controlling mechanism during mitosis or meiosis. The major function of this checkpoint is to ensure chromosomes are properly attached on the kinetochore and separated by the kinetochore microtubules from two spindle poles before entering anaphase.[1] SAC are made up of Aurora B, Bub1, Bub/Mad3 and Mad1, Mad2 and so forth, which can be functionally divided into two groups as protein kinases or non-kinase proteins.[2] The protein kinase, for instant, Aurora B, undergoes phosphorylation, which acts as regulator to activate spindle checkpoint.[3] However, dephosphorylation mostly by protein phosphatase PP1 silences this checkpoint. [4]


  1. Musacchio, A., and Salmon, E. D. (2007). The spindle –assembly checkpoint in space and time. Nat. Rev. Mol. Cell Biol. 8,379-393.
  2. Lesage B., Qian J., and Bollen M. (2011). Spindle checkpoint silencing: PP1 tips the balance. Cell Biology 21, R898-R903, November 8, 2011, 1-2.
  3. Zich, J., and Hardwick, K. G. (2010). Getting down to the phosphorylated ‘nuts and bolts’ of spindle checkpoint signalling. Trends Biochem.SCI.35,18-27.
  4. Vanoosthuyse V., and Hardwick, K.G. (2009). Overcoming inhibition in the spindle checkpoint. Genes Dev.23, 2799-2805.

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