The Zds proteins control entry into mitosis and target protein phosphatase 2A to the Cdc25 phosphatase

Department of Molecular, Cell, and Developmental Biology, Univ. of California, Santa Cruz, CA 95064, USA.
Molecular biology of the cell (Impact Factor: 4.47). 01/2011; 22(1):20-32. DOI: 10.1091/mbc.E10-06-0487
Source: PubMed


The Wee1 kinase restrains entry into mitosis by phosphorylating and inhibiting cyclin-dependent kinase 1 (Cdk1). The Cdc25 phosphatase promotes entry into mitosis by removing Cdk1 inhibitory phosphorylation. Experiments in diverse systems have established that Wee1 and Cdc25 are regulated by protein phosphatase 2A (PP2A), but a full understanding of the function and regulation of PP2A in entry into mitosis has remained elusive. In budding yeast, entry into mitosis is controlled by a specific form of PP2A that is associated with the Cdc55 regulatory subunit (PP2A(Cdc55)). We show here that related proteins called Zds1 and Zds2 form a tight stoichiometric complex with PP2A(Cdc55) and target its activity to Cdc25 but not to Wee1. Conditional inactivation of the Zds proteins revealed that their function is required primarily at entry into mitosis. In addition, Zds1 undergoes cell cycle-dependent changes in phosphorylation. Together, these observations define a role for the Zds proteins in controlling specific functions of PP2A(Cdc55) and suggest that upstream signals that regulate PP2A(Cdc55) may play an important role in controlling entry into mitosis.

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    • "The Mih1 protein is hyperphosphorylated throughout most of the cell cycle in a casein kinase I-dependent manner (Pal et al. 2008), although the contribution of phosphorylation to Mih1 function is not well understood. Only during G2/M transition it is dephosphorylated by Cdc55-dependent PP2A phosphatase with the help of Zds proteins (Pal et al. 2008; Wicky et al. 2011). In addition, Mih1 was reported to be scattered throughout the cell during G2/M and to accumulate in the nucleus during telophase (Keaton et al. 2008). "
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    ABSTRACT: Mitotic cyclin-dependent kinase (CDK) is activated by Cdc25 phosphatase through dephosphorylation at the Wee1-mediated phosphorylation site. In Saccharomyces cerevisiae, regulation of Mih1 (Cdc25 homologue) remains unclear because inactivation/degradation of Swe1 (Wee1 homologue) is the main trigger for G2/M transition. By deleting all mitotic cyclins except Clb2, a strain was created where Mih1 became essential for mitotic entry at high temperatures. Using this novel assay, the essential domain of Mih1 was identified and Mih1 regulation was characterized. Mih1(3E1D) with phosphomimetic substitutions of four putative PKC target residues in Mih1 had a reduced complementation activity, whereas Mih1(4A) with those nonphosphorylatable substitutions was active. The band pattern of Mih1 by SDS-PAGE was similar to that of Mih1(4A) only after inactivation of Pkc1 in a pkc1(ts) mutant. Over-expression of GFP-tagged Mih1 or GFP-Mih1(4A) accumulated as dot-like structures in the nucleus, whereas GFP-Mih1(3E1D) was localized in the cytoplasm. Over-expression of an active form of Pkc1 excluded GFP-Mih1 from the nucleus, but had minimal effect on GFP-Mih1(4A) localization. Furthermore, addition of ectopic nuclear localization signal to the Mih1(3E1D) sequence recovered complementation activity and nuclear localization. These results suggest that Mih1 is negatively regulated by Pkc1-mediated phosphorylation, which excludes it from the nucleus under certain conditions.
    Full-text · Article · Mar 2013 · Genes to Cells
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    • "The Esp1-associated protein Slk19 is necessary for optimal Cdc14 release: while Slk19 is actually cleaved by the protease, this does not seem to be functionally important for the FEAR pathway (Stegmeier et al. 2002). The proteins Zds1 and Zds2, which associate with and regulate PP2A Cdc55 (Yasutis et al. 2010; Wicky et al. 2011) help tip the kinase–phosphatase balance in favor of Cdk1 (Queralt and Uhlmann 2008b). They probably accomplish this by binding and retaining PP2A Cdc55 in the cytoplasm, thereby lowering its nuclear concentration (Rossio and Yoshida 2011), but the precise mechanism remains unclear. "
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    Full-text · Article · Dec 2012 · Genetics
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    • "It has recently been proposed that Zds1 and Zds2 are stoichiometric subunits of the PP2A Cdc55 complex that help regulate its localization and substrate specificity (Rossio and Yoshida, 2011; Wicky et al., 2011). Nuclear levels of PP2A Cdc55 decline slightly in late mitosis, and deletion of both ZDS genes results in the accumulation of Cdc55 in the nucleus (Rossio and Yoshida , 2011). "
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