Cyclin B1-Cdk1 binding to MAD1 links nuclear pore disassembly to chromosomal stability

Abstract

How the cell completely reorganises its architecture when it divides is a problem that has fascinated researchers for almost 150 years. We now know that the core regulatory machinery is highly conserved in eukaryotes but how these multiple protein kinases, protein phosphatases, and ubiquitin ligases are coordinated to remodel the cell in a matter of minutes remains a major question. Cyclin B-CDK is the primary kinase that drives mitotic remodelling and here we show that it is targeted to the nuclear pore complex (NPC) by binding an acidic face of the spindle assembly checkpoint protein, MAD1. This localised Cyclin B1-CDK1 activity coordinates NPC disassembly with kinetochore assembly: it is needed for the proper release of MAD1 from the embrace of TPR at the nuclear pore, which enables MAD1 to be recruited to kinetochores before nuclear envelope breakdown, thereby strengthening the spindle assembly checkpoint to maintain genomic stability.

Mps1-mediated release of Mad1 from nuclear pores ensures the fidelity of chromosome segregation

“…S3, A-D). These results, and the recent observation that Mad1 remains associated with Tpr during early mitosis in reversine-treated RPE cells (Jackman et al, 2019), strongly support that this KT-extrinsic mechanism orchestrated by Mps1 is evolutionarily conserved in vertebrates, where it likely coordinates with Cyclin B1-CDK1 (Jackman et al, 2019) the release of Mad1 from NPCs to enable its proper KT localization.…”

“…S3, A-D). These results, and the recent observation that Mad1 remains associated with Tpr during early mitosis in reversine-treated RPE cells (Jackman et al, 2019), strongly support that this KT-extrinsic mechanism orchestrated by Mps1 is evolutionarily conserved in vertebrates, where it likely coordinates with Cyclin B1-CDK1 (Jackman et al, 2019) the release of Mad1 from NPCs to enable its proper KT localization. Our biochemical, cellular, and in vivo data concur to demonstrate that Mps1 activity at NPCs early in prophase sets the stage to enable appropriate recruitment of Mad1 to unattached/ prometaphase KTs (Fig.…”

PP1 and PP2A Use Opposite Phospho-dependencies to Control Distinct Processes at the Kinetochore

“…This is predicted given that both kinases are recruited to kinetochores in an attachment-sensitive manner (Allan et al., 2019, Jackman et al., 2019, Alfonso-Pérez et al., 2019, Lénárt et al., 2007, Liu et al., 2012). In fact, both are also recruited to the KMN network in a phosphorylation-dependent manner: Cyclin B/CDK1 interacts with Mad1, a phospho-dependent interactor of BUB1, and CDK1 can phosphorylate BUB1 to recruit PLK1 (Allan et al., 2019, Jackman et al., 2019, Alfonso-Pérez et al., 2019, Saurin, 2018). Interestingly, the key Mad1-BUB1 interaction has also been shown to be negatively regulated by kinetochore PP2A-B56 (Qian et al., 2017).…”

Recent advances in understanding the role of Cdk1 in the Spindle Assembly Checkpoint

“…Indeed, it has been shown that kinetochore localization of Mps1, in human cells, greatly depends on direct phosphorylation by Cdk1; thus, Cdk1 controls activity and localization of Mps1 72 . Mps1, in turn, helps kinetochore localization of Cdk1 [73][74][75][76] . As mentioned earlier, by phosphorylating Knl1, Mps1 creates a docking site for kinetochore localization of Bub1, and cooperative Cdk1-and Mps1-dependent phosphorylations of Bub1 are required to recruit Mad1 at kinetochores 42,43,50,59,77 .…”