Journal of Cell Science 115, e2404-e2404 (2002)
Copyright © 2002 The Company of Biologists Limited
Mitotic exit networking
In budding yeast, exit from mitosis is controlled by the mitotic exit
network (MEN). This signalling cascade includes the
guanine-nucleotide-exchange factor Lte1p, its target GTPase (Tem1p), several
protein kinases and ultimately Cdc14p — a dual-specificity phosphatase
that induces mitotic exit by stimulating APC-dependent degradation of mitotic
cyclins. To prevent premature MEN activation, cells initially confine Lte1p to
the bud cortex, away from Tem1p (which localizes to spindle pole bodies),
releasing it after chromosome segregation. Leland Johnston and co-workers now
reveal how this is achieved (see p.
4977). They show that recruitment of Lte1p to the cortex requires the
polarity determinant Cdc42p GTPase (plus its effectors Gic1 and Gic2), which
must first be activated by the cell cycle kinase Cdc28p and its cyclin partner
Cln. Interestingly, Cdc42p cannot substitute for Cdc28p in this process, and
the authors provide evidence that this is because direct phosphorylation of
Lte1p by Cdc28p is also essential. In addition, they demonstrate that Cdc14p
can dephosphorylate Lte1p and trigger its release from the cortex; this could
be the basis for a feedback loop that regulates Lte1p localization and/or
activity.
Related articles in JCS:
- Spatial regulation of the guanine nucleotide exchange factor Lte1 in Saccharomyces cerevisiae
- Sanne Jensen, Marco Geymonat, Anthony L. Johnson, Marisa Segal, and Leland H. Johnston
JCS 2002 115: 4977-4991.
[Abstract]
[Full Text]
