Article
- The EMBO Journal (2007) 26, 4501 - 4513
- doi:10.1038/sj.emboj.7601873
Published online: 4 October 2007
Subject Categories:
Phosphorylation of Bem2p and Bem3p may contribute to local activation of Cdc42p at bud emergence
Michèle Knaus1, Marie-Pierre Pelli-Gulli2,a, Frank van Drogen1, Sander Springer2, Malika Jaquenoud1,a and Matthias Peter1
- Swiss Federal Institute of Technology (ETH), Institute of Biochemistry, ETH Hönggerberg HPM G 6.2, Zürich, Switzerland
- Swiss Institute for Experimental Cancer Research (ISREC), Chemin des Boveresses 155, Epalinges/VD, Switzerland
Correspondence to:
Matthias Peter, Swiss Federal Institute of Technology (ETH), Institute of Biochemistry, ETH Hönggerberg HPM G 6.2, Zürich 8093, Switzerland. Tel.: +41 44 633 6586; Fax: +41 44 632 1298; E-mail: matthias.peter@bc.biol.ethz.ch
aPresent address: Department of Biochemistry, University of Fribourg, Fribourg 1700, Switzerland
Received 1 March 2007; Accepted 10 September 2007
Abstract
Site-specific activation of the Rho-type GTPase Cdc42p is critical for the establishment of cell polarity. Here we investigated the role and regulation of the GTPase-activating enzymes (GAPs) Bem2p and Bem3p for Cdc42p activation and actin polarization at bud emergence in Saccharomyces cerevisiae. Bem2p and Bem3p are localized throughout the cytoplasm and the cell cortex in unbudded G1 cells, but accumulate at sites of polarization after bud emergence. Inactivation of Bem2p results in hyperactivation of Cdc42p and polarization toward multiple sites. Bem2p and Bem3p are hyperphosphorylated at bud emergence most likely by the Cdc28p-Cln2p kinase. This phosphorylation appears to inhibit their GAP activity in vivo, as non-phosphorylatable Bem3p mutants are hyperactive and interfere with Cdc42p activation. Taken together, our results indicate that Bem2p and Bem3p may function as global inhibitors of Cdc42p activation during G1, and their inactivation by the Cdc28p/Cln kinase contributes to site-specific activation of Cdc42p at bud emergence.
Keywords:
- bud emergence,
- Cdc28p,
- Cdc42p,
- cell polarity,
- Cln2p
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