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Molecular and Cellular Biology, November 2000, p. 8548-8559, Vol. 20, No. 22
Department of Microbiology and Molecular
Genetics and Markey Center for Molecular Genetics, University of
Vermont Burlington, Vermont 05405
Received 16 March 2000/Returned for modification 15 May
2000/Accepted 29 August 2000
The Saccharomyces cerevisiae Cdc42p GTPase interacts
with multiple regulators and downstream effectors through an
~25-amino-acid effector domain. Four effector domain mutations, Y32K,
F37A, D38E, and Y40C, were introduced into Cdc42p and characterized for
their effects on these interactions. Each mutant protein showed
differential interactions with a number of downstream effectors and
regulators and various levels of functionality. Specifically,
Cdc42D38Ep showed reduced interactions with the Cla4p
p21-activated protein kinase and the Bem3p GTPase-activating protein
and cdc42D38E was the only mutant allele able
to complement the
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Copyright © 2000, American Society for Microbiology. All rights reserved.
Saccharomyces cerevisiae Cdc42p GTPase Is Involved in
Preventing the Recurrence of Bud Emergence during the Cell
Cycle
cdc42 null mutant. However, the mutant
protein was only partially functional, as indicated by a
temperature-dependent multibudded phenotype seen in conjunction with
defects in both septin ring localization and activation of the
Swe1p-dependent morphogenetic checkpoint. Further analysis of this
mutant suggested that the multiple buds emerged consecutively with a
premature termination of bud enlargement preceding the appearance of
the next bud. Cortical actin, the septin ring, Cla4p-green fluorescent
protein (GFP), and GFP-Cdc24p all predominantly localized to one bud at
a time per multibudded cell. These data suggest that
Cdc42D38Ep triggers a morphogenetic defect post-bud
emergence, leading to cessation of bud growth and reorganization of the
budding machinery to another random budding site, indicating that
Cdc42p is involved in prevention of the initiation of supernumerary
buds during the cell cycle.
*
Corresponding author. Mailing address: Department of
Microbiology and Molecular Genetics, 202 Stafford Hall, University of Vermont, Burlington, VT 05405. Phone: (802) 656-8203. Fax: (802) 656-8749. E-mail: dijohnso{at}zoo.uvm.edu.
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