scholarly journals Roles of Greatwall Kinase in the Regulation of Cdc25 Phosphatase

2008 ◽  
Vol 19 (4) ◽  
pp. 1317-1327 ◽  
Author(s):  
Yong Zhao ◽  
Olivier Haccard ◽  
Ruoning Wang ◽  
Jiangtao Yu ◽  
Jian Kuang ◽  
...  
Keyword(s):  
Protein Kinase ◽  
Xenopus Oocytes ◽  
Mitogen Activated Protein Kinase ◽  
Mitotic Entry ◽  
M Phase ◽  
Egg Extracts ◽  
Mitogen Activated Protein ◽  
Xenopus Egg ◽  
Greatwall Kinase ◽  
Xenopus Egg Extracts

We previously reported that immunodepletion of Greatwall kinase prevents Xenopus egg extracts from entering or maintaining M phase due to the accumulation of inhibitory phosphorylations on Thr14 and Tyr15 of Cdc2. M phase–promoting factor (MPF) in turn activates Greatwall, implying that Greatwall participates in an MPF autoregulatory loop. We show here that activated Greatwall both accelerates the mitotic G2/M transition in cycling egg extracts and induces meiotic maturation in G2-arrested Xenopus oocytes in the absence of progesterone. Activated Greatwall can induce phosphorylations of Cdc25 in the absence of the activity of Cdc2, Plx1 (Xenopus Polo-like kinase) or mitogen-activated protein kinase, or in the presence of an activator of protein kinase A that normally blocks mitotic entry. The effects of active Greatwall mimic in many respects those associated with addition of the phosphatase inhibitor okadaic acid (OA); moreover, OA allows cycling extracts to enter M phase in the absence of Greatwall. Taken together, these findings support a model in which Greatwall negatively regulates a crucial phosphatase that inhibits Cdc25 activation and M phase induction.

scholarly journals Activation of the p42 Mitogen-activated Protein Kinase Pathway Inhibits Cdc2 Activation and Entry into M-Phase in CyclingXenopus Egg Extracts

1998 ◽  
Vol 9 (2) ◽  
pp. 451-467 ◽  
Author(s):  
John C. Bitangcol ◽  
Andrew S.-S. Chau ◽  
Ellamae Stadnick ◽  
Manfred J. Lohka ◽  
Bryan Dicken ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Protein Kinase ◽  
Specific Inhibitor ◽  
Mapk Signaling ◽  
Cyclin B ◽  
Mitogen Activated Protein Kinase ◽  
M Phase ◽  
Egg Extracts ◽  
Mitogen Activated Protein ◽  
Xenopus Egg Extracts

We have added constitutively active MAP kinase/ERK kinase (MEK), an activator of the mitogen-activated protein kinase (MAPK) signaling pathway, to cycling Xenopus egg extracts at various times during the cell cycle. p42MAPK activation during entry into M-phase arrested the cell cycle in metaphase, as has been shown previously. Unexpectedly, p42MAPK activation during interphase inhibited entry into M-phase. In these interphase-arrested extracts, H1 kinase activity remained low, Cdc2 was tyrosine phosphorylated, and nuclei continued to enlarge. The interphase arrest was overcome by recombinant cyclin B. In other experiments, p42MAPK activation by MEK or by Mos inhibited Cdc2 activation by cyclin B. PD098059, a specific inhibitor of MEK, blocked the effects of MEK(QP) and Mos. Mos-induced activation of p42MAPK did not inhibit DNA replication. These results indicate that, in addition to the established role of p42MAPK activation in M-phase arrest, the inappropriate activation of p42MAPK during interphase prevents normal entry into M-phase.

scholarly journals The M Phase Kinase Greatwall (Gwl) Promotes Inactivation of PP2A/B55δ, a Phosphatase Directed Against CDK Phosphosites

2009 ◽  
Vol 20 (22) ◽  
pp. 4777-4789 ◽  
Author(s):  
Priscila V. Castilho ◽  
Byron C. Williams ◽  
Satoru Mochida ◽  
Yong Zhao ◽  
Michael L. Goldberg
Keyword(s):  
Cyclin B ◽  
Regulatory Subunit ◽  
Cyclin Dependent Kinases ◽  
M Phase ◽  
Egg Extracts ◽  
Xenopus Egg ◽  
Greatwall Kinase ◽  
Xenopus Egg Extracts ◽  
Phase Entry ◽  
Dependent Mechanism

We have previously shown that Greatwall kinase (Gwl) is required for M phase entry and maintenance in Xenopus egg extracts. Here, we demonstrate that Gwl plays a crucial role in a novel biochemical pathway that inactivates, specifically during M phase, “antimitotic” phosphatases directed against phosphorylations catalyzed by cyclin-dependent kinases (CDKs). A major component of this phosphatase activity is heterotrimeric PP2A containing the B55δ regulatory subunit. Gwl is activated during M phase by Cdk1/cyclin B (MPF), but once activated, Gwl promotes PP2A/B55δ inhibition with no further requirement for MPF. In the absence of Gwl, PP2A/B55δ remains active even when MPF levels are high. The removal of PP2A/B55δ corrects the inability of Gwl-depleted extracts to enter M phase. These findings support the hypothesis that M phase requires not only high levels of MPF function, but also the suppression, through a Gwl-dependent mechanism, of phosphatase(s) that would otherwise remove MPF-driven phosphorylations.

Protein kinase A acts at multiple points to inhibit Xenopus oocyte maturation

1994 ◽  
Vol 14 (7) ◽  
pp. 4419-4426
Author(s):  
W Matten ◽  
I Daar ◽  
G F Vande Woude
Keyword(s):  
Protein Kinase ◽  
Xenopus Oocytes ◽  
Negative Regulator ◽  
Mitogen Activated Protein Kinase ◽  
Mobility Shift ◽  
Dependent Protein Kinase ◽  
Multiple Points ◽  
Mitogen Activated Protein ◽  
Dependent Protein ◽  
Phosphatase Activation

In Xenopus oocytes, initiation of maturation is dependent on reduction of cyclic AMP-dependent protein kinase (PKA) activity and the synthesis of the mos proto-oncogene product. Mos is required during meiosis I for the activation of both maturation-promoting factor (MPF) and mitogen-activated protein kinase (MAPK). Here we show that injection of the catalytic subunit of PKA (PKAc) prevented progesterone-induced synthesis of endogenous Mos as well as downstream MPF and MAPK activation. However, PKAc did not prevent injected soluble Mos product from activating MAPK. While MAPK is activated during Mos-PKAc coinjection, attendant MPF activation is blocked. Additionally, PKAc caused a potent block in the electrophoretic mobility shift of cdc25 that is associated with phosphatase activation. This inhibition of cdc25 activity was not reversed by progesterone, Mos, or MPF. We conclude that PKAc acts as a negative regulator at several points in meiotic maturation by preventing both Mos translation and MPF activation.

scholarly journals Investigating the determinants of mammalian Mastl kinase activation

2020 ◽  
Author(s):  
Mehmet Erguven ◽  
M. Kasim Diril
Keyword(s):  
Expression System ◽  
Activation Loop ◽  
Middle Region ◽  
Kinase Activation ◽  
Viral Expression ◽  
Egg Extracts ◽  
Xenopus Egg ◽  
Greatwall Kinase ◽  
Xenopus Egg Extracts ◽  
Atypical Member

ABSTRACTMastl (Greatwall) kinase is an essential mitotic protein kinase. Mastl is an atypical member of AGC family with a unique long stretch of non-conserved middle region. The mechanism of its phosphorylation dependent activation has been studied in Xenopus egg extracts, revealing several phosphosites that were suggested to be crucial for kinase activation. These residues correspond to T193 and T206 in the activation loop, and S861 in the C-tail of mouse Mastl. By combining a chemically inducible knockout system to deplete the endogenous Mastl and a viral expression system to ectopically express the mutant variants, we obtained a viable knockout clone that expresses the S861A and S861D mutants. We observed that proliferation rates of the MastlS861A and MastlS861D clones were comparable. Our results have revealed that phosphorylation of the turn motif phosphosite (S861) is auxiliary and it is not indispensable for Mastl function.

scholarly journals Mitogen-activated protein kinase phosphatase 2 regulates histone H3 phosphorylation via interaction with vaccinia-related kinase 1

2013 ◽  
Vol 24 (3) ◽  
pp. 373-384 ◽  
Author(s):  
Min-Woo Jeong ◽  
Tae-Hong Kang ◽  
Wanil Kim ◽  
Yoon Ha Choi ◽  
Kyong-Tai Kim
Keyword(s):  
Protein Kinase ◽  
Histone H3 ◽  
Negative Regulator ◽  
Mitogen Activated Protein Kinase ◽  
H3 Phosphorylation ◽  
Dual Specificity ◽  
Selective Interaction ◽  
M Phase ◽  
Mitogen Activated Protein ◽  
Histone H3 Phosphorylation

Mitogen-activated protein kinase phosphatase 2 (MKP2) is a member of the dual-specificity MKPs that regulate MAP kinase signaling. However, MKP2 functions are still largely unknown. In this study, we showed that MKP2 could regulate histone H3 phosphorylation under oxidative stress conditions. We found that MKP2 inhibited histone H3 phosphorylation by suppressing vaccinia-related kinase 1 (VRK1) activity. Moreover, this regulation was dependent on the selective interaction with VRK1, regardless of its phosphatase activity. The interaction between MKP2 and VRK1 mainly occurred in the chromatin, where histones are abundant. We also observed that the protein level of MKP2 and its interaction with histone H3 increased from G1 to M phase during the cell cycle, which is similar to the VRK1 profile. Furthermore, MKP2 specifically regulated the VRK1-mediated histone H3 phosphorylation at M phase. Taken together, these data suggest a novel function of MKP2 as a negative regulator of VRK1-mediated histone H3 phosphorylation.

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