title: Adaptation to the spindle checkpoint is regulated by the interplay between Cdc28/Clbs and PP2ACdc55.
abstract: The spindle checkpoint arrests cells in metaphase until all chromosomes are properly attached to the chromosome segregation machinery. Thereafter, the anaphase promoting complex (APC/C) is activated and chromosome segregation can take place. Cells remain arrested in mitosis for hours in response to checkpoint activation, but not indefinitely. Eventually, they adapt to the checkpoint and proceed along the cell cycle. In yeast, adaptation requires the phosphorylation of APC/C. Here, we show that the protein phosphatase PP2A(Cdc55) dephosphorylates APC/C, thereby counteracting the activity of the mitotic kinase Cdc28. We also observe that the key regulator of Cdc28, the mitotic cyclin Clb2, increases before cells adapt and is then abruptly degraded at adaptation. Adaptation is highly asynchronous and takes place over a range of several hours. Our data suggest the presence of a double negative loop between PP2A(Cdc55) and APC/C(Cdc20) (i.e., a positive feedback loop) that controls APC/C(Cdc20) activity. The circuit could guarantee sustained APC/C(Cdc20) activity after Clb2 starts to be degraded.
authors.affiliation: FIRC Institute of Molecular Oncology IFOM, 20139 Milan, Italy.
authors.forename: Claudio
authors.initials: C
authors.lastname: Vernieri
authors.forename: Elena
authors.initials: E
authors.lastname: Chiroli
authors.forename: Valentina
authors.initials: V
authors.lastname: Francia
authors.forename: Fridolin
authors.initials: F
authors.lastname: Gross
authors.forename: Andrea
authors.initials: A
authors.lastname: Ciliberto
mesh_terms: D000222:Adaptation, Physiological; D000705:Anaphase; D064173:Anaphase-Promoting Complex-Cyclosome; D017489:CDC28 Protein Kinase, S cerevisiae / Q000037:antagonists & inhibitors / Q000378:metabolism*; D018797:Cell Cycle Proteins / Q000378:metabolism*; D059566:M Phase Cell Cycle Checkpoints; D008954:Models, Biological; D010766:Phosphorylation; D054648:Protein Phosphatase 2 / Q000378:metabolism*; D059748:Proteolysis; D012441:Saccharomyces cerevisiae / Q000166:cytology* / Q000201:enzymology*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*; D059010:Single-Cell Analysis; D043743:Ubiquitin-Protein Ligase Complexes / Q000378:metabolism
chemical_list: C071246:CDC55 protein, S cerevisiae; D018797:Cell Cycle Proteins; D029701:Saccharomyces cerevisiae Proteins; D043743:Ubiquitin-Protein Ligase Complexes; D064173:Anaphase-Promoting Complex-Cyclosome; D017489:CDC28 Protein Kinase, S cerevisiae; D054648:Protein Phosphatase 2