| Title: | The guanine-nucleotide-exchange factor Cdc24p is targeted to the nucleus and polarized growth sites |
| Author(s): | Toenjes KA; Sawyer MM; Johnson DI; |
| Address: | "Department of Microbiology and Molecular Genetics, Markey Center for Molecular Genetics, The University of Vermont, Burlington, Vermont, 05405, USA" |
| DOI: | 10.1016/S0960-9822(00)80022-6 |
| ISSN/ISBN: | 0960-9822 (Print) 0960-9822 (Linking) |
| Abstract: | "Generation of cellular asymmetry or cell polarity plays a critical role in cell-cycle-regulated morphogenetic processes involving the actin cytoskeleton. The GTPase Cdc42 regulates actin rearrangements and signal transduction pathways in all eukaryotic cells [1], and the temporal and spatial regulation of Cdc42p depends on the activity and targeting of its guanine-nucleotide exchange factor (GEF). Cdc24p, the Saccharomyces cerevisiae GEF for Cdc42p, is found in a particulate fraction and localizes to the plasma membrane [2] [3] at sites of polarized growth [4]. We show that Cdc24p labeled with green fluorescent protein (GFP-Cdc24p) was targeted to pre-bud sites, the tips and sides of enlarging buds, and mating projections in pheromone-treated cells. Unexpectedly, GFP-Cdc24p also localized to the nucleus and GFP-Cdc24p levels diminished before nuclear division followed by its reappearance in divided nuclei and mother-bud necks during cytokinesis. The Cdc24p amino-terminal 283 amino acids were necessary and sufficient for nuclear localization, which depended on the cyclin-dependent-kinase inhibitor Far1p. The Cdc24p carboxy-terminal 289 amino acids were necessary and sufficient for targeting to the pre-bud site, bud, mother-bud neck, and mating projection. Targeting was independent of the Cdc24p-binding proteins Far1p, the GTPase Rsr1p/Bud1p, the scaffold protein Bem1p, and the G(beta) subunit Ste4p. These data are consistent with a temporal and spatial regulation of Cdc24p-dependent activation of Cdc42p during the cell cycle" |
| Keywords: | Binding Sites Cell Cycle Cell Cycle Proteins/chemistry/*metabolism Cell Nucleus/metabolism Cell Polarity Cyclin-Dependent Kinases/antagonists & inhibitors DNA-Binding Proteins/metabolism Fungal Proteins/chemistry/*metabolism Green Fluorescent Proteins Gua; |
| Notes: | "MedlineToenjes, K A Sawyer, M M Johnson, D I eng Research Support, Non-U.S. Gov't Research Support, U.S. Gov't, Non-P.H.S. England 1999/10/26 Curr Biol. 1999 Oct 21; 9(20):1183-6. doi: 10.1016/S0960-9822(00)80022-6" |
