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Mol. Cell. Biol., 04 1996, 1376-1390, Vol 16, No. 4
GC Chen, L Zheng and CS Chan
Normal cell growth in the yeast Saccharomyces cerevisiae involves the
selection of genetically determined bud sites where most growth is
localized. Previous studies have shown that BEM2, which encodes a
GTPase-activating protein (GAP) that is specific for the Rho-type GTPase
Rho1p in vitro, is required for proper bud site selection and bud
emergence. We show here that DBM1, which encodes another putative Rho-type
GAP with two tandemly arranged cysteine-rich LIM domains, also is needed
for proper bud site selection, as haploid cells lacking Dbm1p bud
predominantly in a bipolar, rather than the normal axial, manner.
Furthermore, yeast cells lacking both Bem2p and Dbm1p are inviable. The
nonaxial budding defect of dbm1 mutants can be rescued partially by
overproduction of Bem3p and is exacerbated by its absence. Since Bem3p has
previously been shown to function as a GAP for Cdc42p, and also less
efficiently for Rho1p, our results suggest that Dbm1p, like Bem2p and
Bem3p, may function in vivo as a GAP for Cdc42p and/or Rho1p. Both LIM
domains of Dbm1p are essential for its normal function. Point mutations
that alter single conserved cysteine residues within either LIM domain
result in mutant forms of Dbm1p that can no longer function in bud site
selection but instead are capable of rescuing the inviability of bem2
mutants at 35 degrees C.
Copyright © 1996, American Society for Microbiology
The LIM domain-containing Dbm1 GTPase-activating protein is required for normal cellular morphogenesis in Saccharomyces cerevisiae
Department of Microbiology, The University of Texas, Austin, 78712, USA.
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