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Copyright © 2000 Cell Press. All rights reserved.
Molecular Cell, Volume 6, Issue 5, 1155-1167, 1 November 2000
doi:10.1016/S1097-2765(00)00113-1
Article
Phosphorylation of the Cdc42 Exchange Factor Cdc24 by the PAK-like Kinase Cla4 May Regulate Polarized Growth in Yeast
Marie-Pierre Gulli1, Malika Jaquenoud1, Yukiko Shimada1, Guy Niederhäuser1, Philippe Wiget1 and Matthias Peter1, *, *, 
Corresponding author: Matthias Peter, +41 21 692 5884 (phone), +41 21 652 69 33 (fax)Summary
Rho-type GTPases control many cytoskeletal rearrangements, but their regulation remains poorly understood. Here, we show that in S. cerevisiae, activation of the CDK Cdc28-Cln2 at bud emergence triggers relocalization of Cdc24, the GEF for Cdc42, from the nucleus to the polarization site, where it is stably maintained by binding to the adaptor Bem1. Locally activated Cdc42 then polarizes the cytoskeleton in a manner dependent on its effectors Bni1 and the PAK-like kinase Cla4. In addition, Cla4 induces phosphorylation of Cdc24, leading to its dissociation from Bem1 at bud tips, thereby ending polarized bud growth in vivo. Our results thus suggest a dynamic temporal and spatial regulation of the Cdc42 module: Cdc28-Cln triggers actin polarization by activating Cdc42, which in turn restricts its own activation via a negative feedback loop acting on its GEF Cdc24.
