Functional Homology among Human and Fission Yeast Cdc14 Phosphatases

Abstract

Budding and fission yeast Cdc14 homologues, a conserved family of serine-threonine phosphatases, play a role in the inactivation of mitotic cyclin-dependent kinases (CDKs) by molecularly distinct mechanisms. Saccharomyces cerevisiae Cdc14 protein phosphatase inactivates CDKs by promoting mitotic cyclin degradation and the accumulation of a CDK inhibitor to allow budding yeast cells to exit from mitosis. Schizosaccharomyces pombe Flp1 phosphatase down-regulates CDK/cyclin activity, controlling the degradation of the Cdc25 tyrosine phosphatase for fission yeast cells to undergo cytokinesis. In the present work, we show that human Cdc14 homologues (hCdc14A and hCdc14B) rescued flp1-deficient fission yeast strains, indicating functional homology. We also show that hCdc14A and B interacted in vivo with S. pombe Cdc25 and that hCdc14A dephosphorylated this mitotic inducer both in vitro and in vivo. Our results support a Cdc14 conserved inhibitory mechanism acting on S. pombe Cdc25 protein and suggest that human cells may regulate Cdc25 in a similar manner to inactivate Cdk1-mitotic cyclin complexes.

Hippo signalling in the G2/M cell cycle phase: Lessons learned from the yeast MEN and SIN pathways

“…Perhaps Cdc14 can counteract CDK1 activity in mitosis, thereby regulating mitotic exit and cytokinesis. On the basis of the functional conservation between yeast and human Cdc14 [19,20] it seems obvious to assume that fly Cdc14 plays a key role in mitosis and cytokinesis, but as already mentioned there is currently no scientific evidence available that strongly supports this assumption. Hopefully future research will unveil whether and how the fly Cdc14 phosphatase is regulating exit of mitosis.…”

“…Is this also the case in mammalian cells? Considering that human Cdc14 can compensate for the loss of Cdc14 in budding and fission yeast [19,20], the initial answer is a clear yes. However, as is the case for most cellular processes in mammals, the picture is more complicated.…”

“…Intriguingly, the core signalling module of the MEN/SIN is composed of highly conserved members of the Ste20-like kinase family [12][13][14], the MOB co-activator protein family [15], the LATS/NDR kinase family [16,17], and the Cdc14 protein phosphatase family [18]. The MEN/SIN pathway is very highly conserved from yeast to humans, since human Cdc14 can even compensate for the loss of Cdc14 in budding and fission yeast [19,20].…”

Human Cdc14A Reverses CDK1 Phosphorylation of Cdc25A on Serines 115 and 320

“…The constructs for GST-hCdc14A and its phosphatase-inactivating mutant, GST-Cdc14A-CS, with the cysteine 278 mutated to serine, have been described previously. 19 GST-purification was carried out as previously described. 24 The CDK substrates, GST-Cdc25A constructs, were incubated with 2U of Cdk1/cyclin-B1 human complex (New England Biolabs) in kinase buffer (50 mM Tris, pH 7.5, 10 mM MgCl 2 , 1 mM EGTA, 1 mM DTT and 50 mM ATP) in the presence of 0.15 mCi of g( 32 P)ATP for 30´ at 30˚C.…”

“…A few substrates for Cdc14A have been described, and these include Cdh1/Hct1 and INCENP proteins 15,16 and the tumor suppressor p53. 17,18 Moreover, human Cdc14A can rescue flp1/clp1 deficiency and dephosphorylate SpCdc25 protein, 19 suggesting that some conserved mechanisms must exist with the fission yeast Cdc14 homologue. Mammalian cells have three Cdc25 isoforms; Cdc25A, B and C. [20][21][22] All three are dual-specificity phosphatases that activate their physiological substrates, the CDKs, 23 although each Cdc25 family member has unique characteristics and specific roles in cell cycle regulation.…”