The BioGRID | PUBLICATION VIEW

	J. Cell Biol. Mar (2008); 180(5):931-45
Regulation of Mih1-Cdc25 by protein phosphatase 2A and casein kinase 1-
Pal G, Paraz MT, Kellogg DR
Department of Molecular, Cell and Developmental Biology, University of California, Santa Cruz, Santa Cruz, CA 95064, USA-
Abstract: 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-
[PUBMED: 18316413]