A wide variety of cell types delay cell cycle transitions until they reach a critical size threshold, but the mechanisms that measure size and transmit this information to the core cell cycle machinery are largely unknown. Fission yeast cells divide at a specific surface area due to signaling by large, multi-protein structures called ?nodes? at the cortex. Nodes contain conserved cell cycle regulators including the protein kinases Cdr2, Cdr1, and Wee1, which function in a linear, genetically defined pathway to regulate mitotic entry. Recently, we discovered that nodes also contain the conserved GTPase Arf6 and found that Arf6 promotes mitotic entry through the Cdr2- Cdr1-Wee1 pathway. We do not know the mechanisms of assembly or signal transduction within nodes. We will address key open questions using powerful genetic, biochemical, and quantitative imaging approaches. Mutations that abolish node signaling cause cells to divide at a specific volume, as opposed to surface area. Based on several lines of evidence, we hypothesize that regulated accumulation of Cdc25 in the cell nucleus represents the volume sensor. We will test the model that cell size control emerges from different pathways, each monitoring distinct aspects of cell geometry. We will focus on the fundamental process of cell cycle regulation, but our work has broad implications for spatial control of signal transduction because higher-order clusters and node-like structures are emerging as critical sites of signal transduction throughout cell biology.
The specific aims of this grant are to: (1) define the molecular mechanism of Cdr2 node assembly and function, (2) determine how Arf6 GTPase regulates Cdr2 nodes and cell size at division, and (3) test the model that Cdc25 and Cdr2 pathways monitor distinct aspects of cell geometry. Successful completion of these goals will advance scientific knowledge by identifying how defined signaling pathways respond to different aspects of cell growth. Moreover, the signaling mechanisms that we uncover will provide insights for how size controls the activity of other biological systems.
Defects in the mitotic entry control system can lead to genomic instability, a hallmark of cancer. We will use the model organism fission yeast to define of the upstream signals that govern this cell cycle transition. These findings will be important to understand the cellular mechanisms that prevent untimely and inappropriate cell divisions, which contribute to human diseases such as cancer.
|Allard, Corey A H; Opalko, Hannah E; Liu, Ko-Wei et al. (2018) Cell size-dependent regulation of Wee1 localization by Cdr2 cortical nodes. J Cell Biol 217:1589-1599|
|Lee, Mid Eum; Rusin, Scott F; Jenkins, Nicole et al. (2018) Mechanisms Connecting the Conserved Protein Kinases Ssp1, Kin1, and Pom1 in Fission Yeast Cell Polarity and Division. Curr Biol 28:84-92.e4|
|Moseley, James B (2018) Eisosomes. Curr Biol 28:R376-R378|
|Opalko, Hannah E; Moseley, James B (2017) Dynamic regulation of Cdr1 kinase localization and phosphorylation during osmotic stress. J Biol Chem 292:18457-18468|
|Schutt, Katherine L; Moseley, James B (2017) Transient activation of fission yeast AMPK is required for cell proliferation during osmotic stress. Mol Biol Cell 28:1804-1814|
|Moseley, James B (2017) Wee1 and Cdc25: Tools, pathways, mechanisms, questions. Cell Cycle 16:599-600|
|Deng, Lin; Lee, Mid Eum; Schutt, Katherine L et al. (2017) Phosphatases Generate Signal Specificity Downstream of Ssp1 Kinase in Fission Yeast. Mol Cell Biol 37:|
|Zurawel, Ashley A; Kabeche, Ruth; DiGregorio, Sonja E et al. (2016) CAG Expansions Are Genetically Stable and Form Nontoxic Aggregates in Cells Lacking Endogenous Polyglutamine Proteins. MBio 7:|
|Kabeche, Ruth; Madrid, Marisa; Cansado, José et al. (2015) Eisosomes Regulate Phosphatidylinositol 4,5-Bisphosphate (PI(4,5)P2) Cortical Clusters and Mitogen-activated Protein (MAP) Kinase Signaling upon Osmotic Stress. J Biol Chem 290:25960-73|
|Moseley, James B (2015) Cytokinesis: does Mid1 have an identity crisis? Curr Biol 25:R364-6|
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