The Rho-GAP Bem2p plays a GAP-independent role in the morphogenesis checkpoint.
The Saccharomyces cerevisiae morphogenesis checkpoint delays mitosis in response to insults that impair actin organization and/or bud formation. The delay is due to accumulation of the inhibitory kinase Swe1p, which phosphorylates the cyclin-dependent kinase Cdc28p. Having screened through a panel of yeast mutants with defects in cell morphogenesis, we report here that the polarity establishment protein Bem2p is required for the checkpoint response. Bem2p is a Rho-GTPase activating protein (GAP) previously shown to act on Rho1p, and we now show that it also acts on Cdc42p, the GTPase primarily responsible for establishment of cell polarity in yeast. Whereas the morphogenesis role of Bem2p required GAP activity, the checkpoint role of Bem2p did not. Instead, this function required an N-terminal Bem2p domain. Thus, this single protein has a GAP-dependent role in promoting cell polarity and a GAP-independent role in responding to defects in cell polarity by enacting the checkpoint. Surprisingly, Swe1p accumulation occurred normally in bem2 cells, but they were nevertheless unable to promote Cdc28p phosphorylation. Therefore, Bem2p defines a novel pathway in the morphogenesis checkpoint.
Marquitz
Aron R
AR
Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC 27710, USA.
Harrison
Jacob C
JC
Bose
Indrani
I
Zyla
Trevin R
TR
McMillan
John N
JN
Lew
Daniel J
DJ
D000595:Amino Acid Sequence; D001483:Base Sequence; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000494:pharmacology; D017489:CDC28 Protein Kinase, S cerevisiae / Q000502:physiology; D018797:Cell Cycle Proteins; D016764:Cell Polarity; D005656:Fungal Proteins / Q000235:genetics / Q000502:physiology*; D016195:G2 Phase / Q000235:genetics; D020690:GTPase-Activating Proteins / Q000502:physiology*; D005800:Genes, Fungal; D018816:Genes, cdc; D020935:MAP Kinase Signaling System; D008677:Metaphase / Q000235:genetics; D020928:Mitogen-Activated Protein Kinases; D008969:Molecular Sequence Data; D009024:Morphogenesis / Q000235:genetics; D010766:Phosphorylation; D011499:Protein Processing, Post-Translational; D017434:Protein Structure, Tertiary; D017027:Protein Tyrosine Phosphatases / Q000037:antagonists & inhibitors; D011505:Protein-Tyrosine Kinases / Q000502:physiology*; D012100:Reproduction, Asexual; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013844:Thiazoles / Q000494:pharmacology; D053778:Thiazolidines; D020846:cdc42 GTP-Binding Protein, Saccharomyces cerevisiae / Q000502:physiology*; D020666:ras-GRF1
C084219:BEM2 protein, S cerevisiae; D019086:Bridged Bicyclo Compounds, Heterocyclic; C542351:CDC25 protein, S cerevisiae; D018797:Cell Cycle Proteins; D005656:Fungal Proteins; D020690:GTPase-Activating Proteins; D029701:Saccharomyces cerevisiae Proteins; D013844:Thiazoles; D053778:Thiazolidines; D020666:ras-GRF1; C099685:SWE1 protein, S cerevisiae; D011505:Protein-Tyrosine Kinases; D017489:CDC28 Protein Kinase, S cerevisiae; D020928:Mitogen-Activated Protein Kinases; C072724:SLT2 protein, S cerevisiae; D017027:Protein Tyrosine Phosphatases; D020846:cdc42 GTP-Binding Protein, Saccharomyces cerevisiae; C037068:latrunculin B