Abstract
Author SummaryIn budding yeast, cell polarization (or the asymmetric distribution of subcellular components) ensures the targeted transport of proteins and membrane material to the sites of cell growth or cell division in late mitosis. Two conserved members of the Rho-GTPase family, Rho1 and Cdc42, are master regulators of cell polarity. While Rho1 has a well-established role in cytokinesis and cell separation, Cdc42 helps to establish the new polarity site from which the future daughter cell will grow after cytokinesis. Interestingly, despite the fact that Cdc42 is recruited to the site of cell division at the same time as Rho1, the new daughter cell never emerges from the site previously used for cytokinesis during the preceding cell cycle, and it remains elusive how cells coordinate the distinct functions of Rho1 and Cdc42 during cytokinesis. Here, we show that the novel protein Gps1 marks the cell division site, where it maintains Rho1-dependent polarity until cell separation is completed. We also demonstrate that Gps1 prevents activation of Cdc42 at the site of cell division during cytokinesis. We propose that Gps1 provides a novel polarity cue that guides the establishment of a new polarity site, away from the old site of cell division, where the new daughter cell then emerges.
Highlights
Cell polarization, i.e., the asymmetric distribution of subcellular structures and components, is critical for a variety of biological processes in uni- and multicellular organisms [1,2,3]
Cdc42 forms a ring-like structure at the bud neck before actomyosin ring (AMR) contraction, is reorganized as a disc-like structure after AMR constriction, and splits into two well-separated signals just before cell separation (Figures 1 and S1A). This complex pattern of localization at the bud neck during cytokinesis implies that Cdc42 may either perform an important function during cytokinesis or be inhibited during AMR contraction
To understand the regulation and function of Cdc42, we screened for bud neck proteins that interact with Cdc42 using the yeast two-hybrid system
Summary
I.e., the asymmetric distribution of subcellular structures and components, is critical for a variety of biological processes in uni- and multicellular organisms [1,2,3]. The activation of Rho GTPases is under tight spatiotemporal control in response to extra- or intracellular polarity cues (e.g., chemical gradients, cell–cell interactions, or other landmarks) during the establishment and maintenance of cell polarity [4] In this context, membrane-associated proteins often mediate activation or inhibition of Rho GTPases [1,2,4,6]. Membrane-associated proteins often mediate activation or inhibition of Rho GTPases [1,2,4,6] Another feature of polarity establishment and maintenance is that Rho GTPases can be either simultaneously activated at various locations to fulfill different functions (e.g., during cell migration) or sequentially activated at the same location through cross-talk mechanisms (e.g., during single cell wound healing) [5,6]. Both mechanisms require elaborate systems that enable both temporal and spatial separation of Rho GTPase activation
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