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Phosphorylation of Bem2p and Bem3p may contribute to local activation of Cdc42p at bud emergence
Author(s) -
Knaus Michèle,
PelliGulli MariePierre,
van Drogen Frank,
Springer Sander,
Jaquenoud Malika,
Peter Matthias
Publication year - 2007
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1038/sj.emboj.7601873
Subject(s) - library science , sander , art history , humanities , art , engineering , computer science , mechanical engineering
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.