During cell division, chromosome movement and cytokinesis must be precisely coordinated to ensure accurate segregation of chromosomes to daughter cells. Baum and colleagues report the existence of a signalling pathway that triggers polar relaxation — that is, the local softening, at cell poles, of the otherwise rigid actomyosin cortex — which enables cell elongation during anaphase and orderly cell division. Live-cell imaging revealed that actin was cleared from cell poles before furrow formation at the cell equator in Drosophila melanogaster and in human cells. Loss of F-actin and cortical relaxation occurred in response to chromatin coming closer to the poles at mid-anaphase. The authors found that this was dependent on protein phosphatase 1 and its regulatory subunit SDS22, which localize at kinetochores and induce the dephosphorylation and inactivation of ezrin–radixin–moesin proteins, which link actin to the plasma membrane, at the cell poles.
References
Rodrigues, N. T. L. et al. Kinetochore-localized PP1–Sds22 couples chromosome segregation to polar relaxation. Nature http://dx.doi.org/10.1038/nature14496 (2015)
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Baumann, K. Relaxation at the poles. Nat Rev Mol Cell Biol 16, 518 (2015). https://doi.org/10.1038/nrm4083
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DOI: https://doi.org/10.1038/nrm4083