Regulation of Mih1/Cdc25 by protein phosphatase 2A and casein kinase 1

The Cdc25 phosphatase promotes entry into mitosis by removing cyclin-dependent kinase 1 (Cdk1) inhibitory phosphorylation. Previous work suggested that Cdc25 is activated by Cdk1 in a positive feedback loop promoting entry into mitosis; however, it has remained unclear how the feedback loop is initi...

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Bibliographic Details
Published in:The Journal of cell biology 2008-03, Vol.180 (5), p.931-945
Main Authors: Pal, Gayatri, Paraz, Maria T.Z, Kellogg, Douglas R
Format: Article
Language:English
Subjects:
Biochemistry
Casein Kinase I - genetics
Casein Kinase I - metabolism
Cell cycle
Cell Cycle - genetics
Cell cycle proteins
Cell Cycle Proteins - genetics
Cell Cycle Proteins - metabolism
Cell Differentiation - genetics
Cell Enlargement
Cell growth
Cell Polarity - genetics
Cellular biology
Fungal Proteins - genetics
Fungal Proteins - metabolism
Gene expression regulation
Gene Expression Regulation, Fungal - genetics
Genes, cdc - physiology
Kinases
Mitosis
Mitosis - genetics
Phosphatases
Phosphorylation
Protein Phosphatase 2 - genetics
Protein Phosphatase 2 - metabolism
Protein Tyrosine Phosphatases - genetics
Protein Tyrosine Phosphatases - metabolism
Proteins
ras-GRF1 - genetics
ras-GRF1 - metabolism
Saccharomyces cerevisiae
Saccharomyces cerevisiae - enzymology
Saccharomyces cerevisiae - genetics
Saccharomyces cerevisiae Proteins - genetics
Saccharomyces cerevisiae Proteins - metabolism
Saccharomycetales
Signal Transduction - genetics
Western blotting
Yeasts
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Summary:The Cdc25 phosphatase promotes entry into mitosis by removing cyclin-dependent kinase 1 (Cdk1) inhibitory phosphorylation. Previous work suggested that Cdc25 is activated by Cdk1 in a positive feedback loop promoting entry into mitosis; however, it has remained unclear how the feedback loop is initiated. To learn more about the mechanisms that regulate entry into mitosis, we have characterized the function and regulation of Mih1, the budding yeast homologue of Cdc25. We found that Mih1 is hyperphosphorylated early in the cell cycle and is dephosphorylated as cells enter mitosis. Casein kinase 1 is responsible for most of the hyperphosphorylation of Mih1, whereas protein phosphatase 2A associated with Cdc55 dephosphorylates Mih1. Cdk1 appears to directly phosphorylate Mih1 and is required for initiation of Mih1 dephosphorylation as cells enter mitosis. Collectively, these observations suggest that Mih1 regulation is achieved by a balance of opposing kinase and phosphatase activities. Because casein kinase 1 is associated with sites of polar growth, it may regulate Mih1 as part of a signaling mechanism that links successful completion of growth-related events to cell cycle progression.
ISSN:0021-9525
1540-8140
DOI:10.1083/jcb.200711014