Identification of Candidate Cyclin-dependent kinase 1 (Cdk1) Substrates in Mitosis by Quantitative Phosphoproteomics

Abstract

An important objective of a cell is to accurately replicate its genetic material and evenly divide along with its subcellular components into two identical daughter cells. To do so, a cell reduces or halts growth, transcription, cap-dependent translation, and undergoes dramatic changes in cellular structure and organization. These changes include chromosome condensation, nuclear envelope breakdown, disassembly of the endoplasmic reticulum and Golgi apparatus, reorganization of the actin cortex, and the formation of the mitotic spindle. Deregulation and errors in these processes can produce nonidentical daughter cells with aberrant chromosome numbers, a state known as aneuploidy and a hallmark of human cancer and the origin of many birth defects (1-5). Therefore, it is imperative that mitosis proceeds in a highly accurate and controlled manner. This is achieved by a sophisticated network of proteins that engage in a multitude of protein-protein interactions regulated by post-translational modifications, including dynamic protein phosphorylation by protein kinases and phosphatases (summarized in (6 -8)).One of the master regulators of mitosis that is conserved from yeast to human is the cyclin-dependent kinase 1 (Cdk1) 1 (9). Cdk1 expression is constant across the cell cycle and the regulation of its activity relies on its association with cyclin A and B, as well as on post-translational modifications including phosphorylation. Specifically, mRNA and protein abundance of cyclin A and B oscillate during the cell cycle due to temporally regulated transcription, translation, and degradation cycles that restrict Cdk1 activity from S-phase to mitosis

Mitotic exit is controlled during anaphase by an Aurora B-Cyclin B1/Cdk1 crosstalk

“…In concert with previous work , our findings unveil an unexpected crosstalk between molecular "rulers" inactivation promotes the recruitment of PP1 phosphatase to chromosomes to locally oppose Aurora B phosphorylation (Qian et al, 2015) and recent findings in budding yeast demonstrating equivalent phosphorylation and dephosphorylation events during mitotic exit (Touati et al, 2018). Moreover, it provides an explanation for the coordinated action of two unrelated protein kinases that likely regulate multiple substrates required for mitotic exit (Afonso et al, 2017;Kettenbach et al, 2011;Petrone et al, 2016).…”

Cell adhesion is regulated by CDK1 during the cell cycle

“…These data demonstrate that the controlled modification of either cell-ECM adhesion or the actin cytoskeleton in G2 is essential to allow cells to pass through mitosis accurately and that, consistent with previous observations (Dao et al, 2009;Lancaster et al, 2013;Marchesi et al, 2014), manipulations that prevent adhesion complex disassembly before mitosis reduce the ability of cells to divide efficiently. CDK1 kinase activity is required to maintain adhesion complexes in interphase CDK1 is a promiscuous serine/threonine kinase that can phosphorylate hundreds of proteins, with a great number of these being involved in regulation of cellular architecture (Olsen et al, 2010;Petrone et al, 2016). Based on phosphoproteomic analyses, adhesion complexes contain a range of potential mitotic kinase phosphorylation sites, raising the possibility that these enzymes might regulate adhesion directly (Robertson et al, 2015).…”

Two-step interphase microtubule disassembly aids spindle morphogenesis

“…Cdk1/CyclinB complex activity rises at around the time that interphase microtubules begin to depolymerize [26]. Since Cdk1/CyclinB is thought to mediate many of the structural changes that accompany entry into the mitosis, including microtubule cytoskeleton remodelling [28–32]), in our search for regulators of this loss of interphase microtubules at the entry into mitosis, we focused our attention on conserved regulators of microtubules that are potential substrates of Cdk1/CyclinB. This led us to explore the function of Ensconsin in this system.…”

“…It is generally assumed that the differences in microtubule structure and dynamics that accompany the transition from interphase to mitosis result from phosphorylation-induced changes in the activities and/or binding capacities of stabilizing and destabilizing microtubule-associated proteins (MAPs) downstream of Cdk1/CyclinB activation [28–32]. However, given the gradual increase in Cdk1/CyclinB complex activity [21], it is hard to reconcile this view with the switch-like change in overall levels of microtubule polymer, which are reported to occur during the transition from prophase to prometaphase [6].…”