Polarity establishment and oriented cell divisions are central to the development of many organisms. Cells of the budding yeast S. cerev/s/ae exhibit two distinct patterns of budding depending on their cell type, reflecting genetic programming of cell polarization. It is believed that a cell responds to a cell-type-specific cortical marker, which is associated with the plasma membrane. All cell types use a common downstream pathway for polarity establishment, which involves the Ras and Rho family GTPases Rsr1/Bud1 and Cdc42. Despite current knowledge of many proteins involved in budding, how polarity is established toward a spatially defined site is largely unknown. This proposal focuses on how a macromolecular complex that specifies a specific bud site is assembled, and how polarity establishment is controlled in a spatial and temporal manner. Based on genetic and biochemical data, it is hypothesized that GTPases regulate various steps of polarity establishment. To test the hypothesis, multi-directional approaches will be undertaken using molecular genetic, biochemical, and cell biological methods.
Specific aims are to understand: 1) How a macromolecular complex that specifies a bud site is assembled and how the transient spatial information is inherited in every cell division cycle;2) how Bud2 and Bud5, regulators for Rsr1, interact with a distinct spatial landmark in each cell type, and whether the interactions regulate their activity; and 3) how Rsr1 regulates Cdc24, a GEF for Cdc42, and assembly of the Cdc42 complex at the bud site. Although polarity establishment is a complex problem, the facile genetics of yeast provides the unique opportunity to study a signaling pathway leading to polarized organization of the actin cytoskeleton at the molecular level. Development of mammalian cells also requires continual changes in the actin cytoskeleton in response to internal and external signals as seen during wound healing or chemotaxis during infection. Understanding the molecular mechanism underlying polarity establishment in yeast is expected to provide the molecular basis of actin cytoskeleton organization in mammalian cells. Given the structural and functional conservation of GTPases and their regulators in eukaryotes, knowledge gained will also allow an insight into novel mechanisms for these critical regulators of normal development, which is expected to relevant to most eukaryotes including humans.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM076375-04
Application #
7576088
Study Section
Cell Structure and Function (CSF)
Program Officer
Deatherage, James F
Project Start
2006-01-01
Project End
2011-12-31
Budget Start
2009-01-01
Budget End
2011-12-31
Support Year
4
Fiscal Year
2009
Total Cost
$282,199
Indirect Cost
Name
Ohio State University
Department
Genetics
Type
Schools of Arts and Sciences
DUNS #
832127323
City
Columbus
State
OH
Country
United States
Zip Code
43210
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Bi, Erfei; Park, Hay-Oak (2012) Cell polarization and cytokinesis in budding yeast. Genetics 191:347-87
Nelson, Scott A; Sanson, Anthony M; Park, Hay-Oak et al. (2012) A novel role for the GTPase-activating protein Bud2 in the spindle position checkpoint. PLoS One 7:e36127

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