Genetics. Published Articles Ahead of Print: July 2, 2006, Copyright © 2006
doi:10.1534/genetics.106.058180


A more recent version of this article appeared on October 1, 2006.

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Four novel suppressors of gic1 gic2 and their roles in cytokinesis and polarized cell growth in S. cerevisiae

Meghal Gandhi 1*, Bruce L. Goode 1 and Clarence S.M. Chan 2

1 Brandeis University
2 University of Texas at Austin

* To whom correspondence should be addressed. E-mail: meghal{at}brandeis.edu.

Submitted on March 14, 2006
Revised on April 5, 2006
Accepted on 23 June 2006


Abstract

Gic1 and Gic2 are two CRIB (Cdc42-Rac interactive binding) domain-containing effectors of Cdc42-GTPase that promote polarized cell growth in S. cerevisiae. To identify novel genes that functionally interact with Gic1 and Gic2, we screened for high-copy suppressors of a gic1 gic2 temperature sensitive strain. We identified two pairs of structurally related genes, SKG6-TOS2 and VHS2-MLF3. These genes have been implicated in polarized cell growth, but their functions have not previously been characterized. We found that overproduction of Skg6 and Tos2 in wild-type cells causes aberrant localization of Cdc3 septin and actin structures as well as defective recruitment of Hof1 and impaired formation of the septum at the mother-bud neck. These data suggest a negative regulatory function for Skg6 and Tos2 in cytokinesis. Consistent with this model, deletion of SKG6 suppresses the growth defects associated with loss of HOF1, a positive regulator of cytokinesis. Our analysis of the second pair of gic1 gic2 suppressors, VHS2 and MLF3, suggest that they regulate polarization of the actin cytoskeleton and cell growth and function in a pathway distinct from and parallel to GIC1 and GIC2.

Key Words: Gic1 Gic2, Hof1, actin, cell wall, cytokinesis