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Mol. Cell. Biol., 06 1997, 3429-3439, Vol 17, No. 6
T Chen and J Kurjan
SST2 plays an important role in the sensitivity of yeast cells to pheromone
and in recovery from pheromone-induced G1 arrest. Recently, a family of
Sst2p homologs that act as GTPase-activating proteins (GAPs) for G alpha
subunits has been identified. We have identified an interaction between
Sst2p and the previously identified Mpt5p by using the two-hybrid system.
Loss of Mpt5p function resulted in a temperature- sensitive growth
phenotype, an increase in pheromone sensitivity, and a defect in recovery
from pheromone-induced G1 arrest, although the effects on pheromone
response and recovery were mild in comparison to those of sst2 mutants.
Overexpression of either Sst2p or Mpt5p promoted recovery from G1 arrest.
Promotion of recovery by overexpression of Mpt5p required Sst2p, but the
effect of overexpression of Sst2p was only partially dependent on Mpt5p.
Mpt5p was also found to interact with the mitogen-activated protein kinase
homologs Fus3p and Kss1p, and an mpt5 mutation was able to suppress the
pheromone arrest and mating defects of a fus3 mutant. Because either mpt5
or cln3 mutations suppressed the fus3 phenotypes, interactions of Mpt5p
with the G1 cyclins and Cdc28p were tested. An interaction between Mpt5p
and Cdc28p was detected. We discuss these results with respect to a model
in which Sst2p plays a role in pheromone sensitivity and recovery that acts
through Mpt5p in addition to a role as a G alpha GAP suggested by the
analysis of the Sst2p homologs.
Copyright © 1997, American Society for Microbiology
Saccharomyces cerevisiae Mpt5p interacts with Sst2p and plays roles in pheromone sensitivity and recovery from pheromone arrest
Department of Microbiology and Molecular Genetics, College of Medicine, University of Vermont, Burlington 05405-0068, USA.
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