Accurate chromosome segregation is vital for cell proliferation, tissue homeostasis, embryonic development, and tumor suppression. One key regulatory pathway is the spindle assembly checkpoint (SAC), which prevents the separation of sister chromatids and exit from mitosis until all chromosomes are linked to both spindle poles by microtubule fibers. Even a single chromosome lacking bipolar attachment is sufficient to trigger the SAC, as its kinetochores recruit and activate downstream factors that not only communicate with the core cell-cycle machinery, but also alter the microtubule-binding properties of the kinetochore itself, so that incorrect microtubule attachments are destabilized. Recent work from our lab has implicated the protein kinase Mps1 in both of these outputs, as well as in a third pathway that acts as a mitotic 'clock'or 'timer'independently of kinetochores. These insights emerged through combined application of gene editing and chemical genetics techniques pioneered in our lab, whereby endogenous Mps1 in cultured human cells was deleted from the genome and replaced by a variant kinase allele sensitized to bulky purine analogs. Using this system, we have performed global and targeted proteomics screens and generated an extensive suite of phosphospecific antibodies, revealing the landscape of Mps1-dependent phosphorylation at the kinetochore-microtubule interface.
In Aim 1, we will mine this information to analyze how Mps1 and counteracting phosphatases regulate kinetochore-microtubule attachments, such that only proper bipolar attachments are stabilized.
In Aim 2, we dissect how Mps1-catalyzed phosphorylation fuels the recruitment and activation of SAC effectors at kinetochores, resulting in the production of biochemical inhibitors of the APC/C-Cdc20 ubiquitin ligase.
In Aim 3, we use chemical genetics to ask how Mps1 and other kinases interact to maintain the M phase state when the SAC is engaged. These studies will illuminate the molecules and mechanisms underlying M phase quality control, and in the long term will empower development of therapeutic agents that target aneuploidy-associated diseases such as cancer.

Public Health Relevance

Errors in transmitting chromosomes to dividing cells are strongly linked to human diseases, including infertility, spontaneous miscarriages, birth defects, and malignancy. The studies in this project seek to understand how the process of chromosome transmission is controlled at the molecular level. This information is necessary to understand how errors in chromosome transmission arise in the course of disease, and to develop new therapies that exploit this trait as an Achilles heel of most cancer cells, providing more effective and less toxic cures for this disorder.

National Institute of Health (NIH)
Research Project (R01)
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Cellular Signaling and Regulatory Systems Study Section (CSRS)
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Hamlet, Michelle R
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Rodriguez-Bravo, Veronica; Maciejowski, John; Corona, Jennifer et al. (2014) Nuclear pores protect genome integrity by assembling a premitotic and Mad1-dependent anaphase inhibitor. Cell 156:1017-31
Oppermann, Felix S; Grundner-Culemann, Kathrin; Kumar, Chanchal et al. (2012) Combination of chemical genetics and phosphoproteomics for kinase signaling analysis enables confident identification of cellular downstream targets. Mol Cell Proteomics 11:O111.012351
Burkard, Mark E; Santamaria, Anna; Jallepalli, Prasad V (2012) Enabling and disabling polo-like kinase 1 inhibition through chemical genetics. ACS Chem Biol 7:978-81
Sherwood, Rebecca; Takahashi, Tatsuro S; Jallepalli, Prasad V (2010) Sister acts: coordinating DNA replication and cohesion establishment. Genes Dev 24:2723-31
Maciejowski, John; George, Kelly A; Terret, Marie-Emilie et al. (2010) Mps1 directs the assembly of Cdc20 inhibitory complexes during interphase and mitosis to control M phase timing and spindle checkpoint signaling. J Cell Biol 190:89-100