APC/C-mediated proteolysis of cyclin B and securin promotes anaphase entry, inactivating CDK1 and permitting chromosome segregation, respectively. Reduction of CDK1 activity relieves inhibition of the CDK1-counteracting phosphatases PP1 and PP2A-B55, allowing wide-spread dephosphorylation of substrates. Meanwhile, continued APC/C activity promotes proteolysis of other mitotic regulators. Together, these activities orchestrate a complex series of events during mitotic exit. However, the relative importance of regulated proteolysis and dephosphorylation in dictating the order and timing of these events remains unclear. Using high temporal-resolution proteomics, we compare the relative extent of proteolysis and protein dephosphorylation. This reveals highly-selective rapid proteolysis of cyclin B, securin and geminin at the metaphase-anaphase transition, followed by slow proteolysis of other substrates. Dephosphorylation requires APC/C-dependent destruction of cyclin B and was resolved into PP1-dependent categories with unique sequence motifs. We conclude that dephosphorylation initiated by selective proteolysis of cyclin B drives the bulk of changes observed during mitotic exit.
Source data files have been provided for Figures 2, 3, 6 and 7. These include a processed form of the raw data, where some extraneous metadata has been removed.Full raw data is available at PRIDE with the following accession numbers: FIgure 2 Total Proteome PXD019791, Figure 2 Phospho-proteome PXD019788, Figure 3 PXD019795, Figure 6 PXD019787, Figure 7 PXD019786
CDK1-CCNB1 creates a spindle checkpoint-permissive state by enabling MPS1 kinetochore localizationhttps://www.ncbi.nlm.nih.gov/pmc/articles/PMC6446832/.
- James Holder
- Francis A Barr
- James Holder
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
- Adèle L Marston, University of Edinburgh, United Kingdom
© 2020, Holder et al.
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