Control of Lte1 localization by cell polarity determinants and Cdc14.
BACKGROUND
The putative guanine nucleotide exchange factor Lte1 plays an essential role in promoting exit from mitosis at low temperatures. Lte1 is thought to activate a Ras-like signaling cascade, the mitotic exit network (MEN). MEN promotes the release of the protein phosphatase Cdc14 from the nucleolus during anaphase, and this release is a prerequisite for exit from mitosis. Lte1 is present throughout the cell during G1 but is sequestered in the bud during S phase and mitosis by an unknown mechanism.


RESULTS
We show that anchorage of Lte1 in the bud requires septins, the cell polarity determinants Cdc42 and Cla4, and Kel1. Lte1 physically associates with Kel1 and requires Kel1 for its localization in the bud, suggesting a role for Kel1 in anchoring Lte1 at the bud cortex. Our data further implicate the PAK-like protein kinase Cla4 in controlling Lte1 phosphorylation and localization. CLA4 is required for Lte1 phosphorylation and bud localization. Furthermore, when overexpressed, CLA4 induces Lte1 phosphorylation and localization to regions of polarized growth. Finally, we show that Cdc14, directly or indirectly, controls Lte1 dephosphorylation and delocalization from the bud during exit from mitosis.


CONCLUSIONS
Restriction of Lte1 to the bud cortex depends on the cortical proteins Cdc42 and Kel1 and the septin ring. Cla4 and Cdc14 promote and demote Lte1 localization at and from the bud cortex, respectively, suggesting not only that the phosphorylation status of Lte1 controls its localization but also indicating that Cla4 and Cdc14 are key regulators of the spatial asymmetry of Lte1.
Seshan
Anupama
A
Center for Cancer Research, Howard Hughes Medical Institute, Massachusetts Institute of Technology, E17-233, 40 Ames Street, Cambridge, Massachusetts 02139, USA.
Bardin
Allison J
AJ
Amon
Angelika
A
D000199:Actins / Q000378:metabolism; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000494:pharmacology; D029742:Caenorhabditis elegans Proteins; D018797:Cell Cycle Proteins / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D016764:Cell Polarity / Q000187:drug effects / Q000502:physiology*; D003593:Cytoplasm / Q000378:metabolism; D003598:Cytoskeletal Proteins / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D003599:Cytoskeleton / Q000378:metabolism; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism; D015966:Gene Expression Regulation, Fungal; D020662:Guanine Nucleotide Exchange Factors / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D008870:Microtubules / Q000378:metabolism; D008938:Mitosis; D009154:Mutation; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism; D021381:Protein Transport; D017027:Protein Tyrosine Phosphatases / Q000235:genetics / Q000378:metabolism*; D011506:Proteins / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000166:cytology* / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D013844:Thiazoles / Q000494:pharmacology; D053778:Thiazolidines; D020846:cdc42 GTP-Binding Protein, Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism
D000199:Actins; D019086:Bridged Bicyclo Compounds, Heterocyclic; C099504:CDC12 protein, S cerevisiae; C074860:CDC14 protein, S cerevisiae; D029742:Caenorhabditis elegans Proteins; D018797:Cell Cycle Proteins; D003598:Cytoskeletal Proteins; D005656:Fungal Proteins; D020662:Guanine Nucleotide Exchange Factors; C089357:LTE1 protein, S cerevisiae; D011506:Proteins; D029701:Saccharomyces cerevisiae Proteins; D013844:Thiazoles; D053778:Thiazolidines; C121715:kel-1 protein, C elegans; C095212:CLA4 protein, S cerevisiae; D017346:Protein Serine-Threonine Kinases; D017027:Protein Tyrosine Phosphatases; D020846:cdc42 GTP-Binding Protein, Saccharomyces cerevisiae; C037067:latrunculin A