scholarly journals cdc25 is one of the MPM-2 antigens involved in the activation of maturation-promoting factor.

1994 ◽  
Vol 5 (2) ◽  
pp. 135-145 ◽  
Author(s):  
J Kuang ◽  
C L Ashorn ◽  
M Gonzalez-Kuyvenhoven ◽  
J E Penkala
Keyword(s):  
Monoclonal Antibody ◽  
Xenopus Oocytes ◽  
Cdc2 Kinase ◽  
Kinase Activation ◽  
Positive Regulator ◽  
Egg Extract ◽  
M Phase ◽  
Important Regulator ◽  
Maturation Promoting Factor

MPM-2 antigens, a discrete set of phosphoproteins that contain similar phosphoepitopes recognized by the monoclonal antibody MPM-2, are phosphorylated during M-phase induction. Our previous studies suggested that certain MPM-2 antigens are involved in the appearance of maturation-promoting factor (MPF) activity. Because the central mitotic regulator cdc2 kinase has been shown to exhibit MPF activity, we explored the possibility that certain MPM-2 antigens are regulators of cdc2 kinase. We found that MPM-2 binding of its antigens would inhibit the autoamplification of cdc2 kinase in Xenopus oocytes and interfere with cyclin-activation of cdc2 kinase in Xenopus interphase egg extract. Immunodepletion of MPM-2 antigens from cyclin-induced M-phase egg extract caused the inactivation of cdc2 kinase, which was accompanied by an inhibitory phosphorylation of p34cdc2 on Thr 14 and Tyr 15, indicating that at least one MPM-2 antigen is a positive regulator of p34cdc2 dephosphorylation. We then showed that cdc25 from M-phase arrested egg extract is an MPM-2 antigen. These results suggest that phosphorylation of the epitope recognized by MPM-2 may be a crucial event in the activation of cdc25 and that the kinase(s) that phosphorylates this MPM-2 epitope may be an important regulator of cdc2 kinase activation.

Inactivation of the checkpoint kinase Cds1 is dependent on cyclin B-Cdc2 kinase activation at the meiotic G2/M-phase transition in Xenopus oocytes

2001 ◽  
Vol 114 (18) ◽  
pp. 3397-3406
Author(s):  
Tetsuya Gotoh ◽  
Keita Ohsumi ◽  
Tomoko Matsui ◽  
Haruhiko Takisawa ◽  
Takeo Kishimoto
Keyword(s):  
Phase Transition ◽  
Xenopus Oocytes ◽  
Cyclin B ◽  
Cdc2 Kinase ◽  
Kinase Activation ◽  
Immature Oocytes ◽  
Protein Levels ◽  
M Phase ◽  
G2 Phase

Checkpoint controls ensure chromosomal integrity through the cell cycle. Chk1 and Cds1/Chk2 are effector kinases in the G2-phase checkpoint activated by damaged or unreplicated DNA, and they prevent entry into M-phase through inhibition of cyclin B-Cdc2 kinase activation. However, little is known about how the effector kinases are regulated when the checkpoint is attenuated. Recent studies indicate that Chk1 is also involved in the physiological G2-phase arrest of immature Xenopus oocytes via direct phosphorylation and inhibition of Cdc25C, the activator of cyclin B-Cdc2 kinase. Bearing in mind the overlapping functions of Chk1 and Cds1, here we have studied the involvement of Xenopus Cds1 (XCds1) in the G2/M-phase transition of immature oocytes and the regulation of its activity during this period. Protein levels of XCds1 remained constant throughout oocyte maturation and early embryonic development. The levels of XCds1 kinase activity were high in immature oocytes and decreased at the meiotic G2/M-phase transition. Consistently, when overexpressed in immature oocytes, wild-type, but not kinase-deficient, XCds1 significantly delayed entry into M-phase after progesterone treatment. The inactivation of XCds1 depended on the activation of cyclin B-Cdc2 kinase, but not MAP kinase. Although XCds1 was not directly inactivated by cyclin B-Cdc2 kinase in vitro, XCds1 was inactivated by overexpression of cyclin B, which induces the activation of cyclin B-Cdc2 kinase without progesterone. Thus, the present study is the first indication of Cds1 activity in cells that are physiologically arrested at G2-phase, and of its downregulation at entry into M-phase.

Inhibiting proteasome activity causes overreplication of DNA and blocks entry into mitosis in sea urchin embryos

2000 ◽  
Vol 113 (15) ◽  
pp. 2659-2670 ◽  
Author(s):  
H. Kawahara ◽  
R. Philipova ◽  
H. Yokosawa ◽  
R. Patel ◽  
K. Tanaka ◽  
...  
Keyword(s):  
Sea Urchin ◽  
Embryonic Cell ◽  
S Phase ◽  
Cdc2 Kinase ◽  
Replication Checkpoint ◽  
Kinase Activation ◽  
Peptide Aldehydes ◽  
M Phase ◽  
Dna Replication Checkpoint ◽  
P34 Cdc2

The proteasome has been shown to be involved in exit from mitosis by bringing about destruction of mitotic cyclins. Here, we present evidence that the proteasome is also required for proper completion of S phase and for entry into mitosis in the sea urchin embryonic cleavage cycle. A series of structurally related peptide-aldehydes prevent nuclear envelope breakdown in their order of inhibitory efficacies against the proteasome. Their efficacies in blocking exit from S phase and exit from mitosis correlate well, indicating that the proteasome is involved at both these steps. Mitotic histone HI kinase activation and tyrosine dephosphorylation of p34(cdc2) kinase are blocked by inhibition of the proteasome, indicating that the proteasome plays an important role in the pathway that leads to embryonic p34(cdc2)kinase activation. Arrested embryos continued to incorporate [(3)H]thymidine and characteristically developed large nuclei. Pre-mitotic arrest can be overcome by treatment with caffeine, a manoeuvre that is known to override the DNA replication checkpoint. These data demonstrate that the proteasome is involved in the control of termination of S phase and consequently in the initiation of M phase of the first embryonic cell cycle.

scholarly journals Periodic changes in phosphorylation of the Xenopus cdc25 phosphatase regulate its activity.

1992 ◽  
Vol 3 (8) ◽  
pp. 927-939 ◽  
Author(s):  
T Izumi ◽  
D H Walker ◽  
J L Maller
Keyword(s):  
Tyrosine Phosphatase ◽  
Mitotic Cell ◽  
Cdc25 Phosphatase ◽  
Mobility Shift ◽  
Cdc2 Kinase ◽  
Kinase Activation ◽  
Cell Cycles ◽  
M Phase ◽  
Egg Extracts ◽  
Cdc25 Protein

The cdc25 tyrosine phosphatase is known to activate cdc2 kinase in the G2/M transition by dephosphorylation of tyrosine 15. To determine how entry into M-phase in eukaryotic cells is controlled, we have investigated the regulation of the cdc25 protein in Xenopus eggs and oocytes. Two closely related Xenopus cdc25 genes have been cloned and sequenced and specific antibodies generated. The cdc25 phosphatase activity oscillates in both meiotic and mitotic cell cycles, being low in interphase and high in M-phase. Increased activity of cdc25 at M-phase is accompanied by increased phosphorylation that retards electrophoretic mobility in gels from 76 to 92 kDa. Treatment of cdc25 with either phosphatase 1 or phosphatase 2A removes phosphate from cdc25, reverses the mobility shift, and decreases its ability to activate cdc2 kinase. Furthermore, the addition of okadaic acid to egg extracts arrested in S-phase by aphidicolin causes phosphorylation and activation of the cdc25 protein before cyclin B/cdc2 kinase activation. These results demonstrate that the activity of the cdc25 phosphatase at the G2/M transition is directly regulated through changes in its phosphorylation state.

scholarly journals Phosphorylation of p21 in G2/M Promotes Cyclin B-Cdc2 Kinase Activity

2005 ◽  
Vol 25 (8) ◽  
pp. 3364-3387 ◽  
Author(s):  
Bipin C. Dash ◽  
Wafik S. El-Deiry
Keyword(s):  
Kinase Activity ◽  
Cyclin B1 ◽  
S Phase ◽  
Cdk Inhibitor ◽  
Wild Type ◽  
Cdc2 Kinase ◽  
Dependent Protein Kinase ◽  
Kinase Activation ◽  
M Phase ◽  
Dependent Protein

ABSTRACT Little is known about the posttranslational control of the cyclin-dependent protein kinase (CDK) inhibitor p21. We describe here a transient phosphorylation of p21 in the G2/M phase. G2/M-phosphorylated p21 is short-lived relative to hypophosphorylated p21. p21 becomes nuclear during S phase, prior to its phosphorylation by CDK2. S126-phosphorylated cyclin B1 binds to T57-phosphorylated p21. Cdc2 kinase activation is delayed in p21-deficient cells due to delayed association between Cdc2 and cyclin B1. Cyclin B1-Cdc2 kinase activity and G2/M progression in p21−/− cells are restored after reexpression of wild-type but not T57A mutant p21. The cyclin B1 S126A mutant exhibits reduced Cdc2 binding and has low kinase activity. Phosphorylated p21 binds to cyclin B1 when Cdc2 is phosphorylated on Y15 and associates poorly with the complex. Dephosphorylation on Y15 and phosphorylation on T161 promotes Cdc2 binding to the p21-cyclin B1 complex, which becomes activated as a kinase. Thus, hyperphosphorylated p21 activates the Cdc2 kinase in the G2/M transition.

Dissociation of MAP kinase activation and MPF activation in hormone-stimulated maturation of Xenopus oocytes

Development ◽  
1999 ◽  
Vol 126 (20) ◽  
pp. 4537-4546 ◽  
Author(s):  
D.L. Fisher ◽  
T. Brassac ◽  
S. Galas ◽  
M. Doree
Keyword(s):  
Map Kinase ◽  
Xenopus Oocytes ◽  
Kinase Activity ◽  
Early Response ◽  
Meiotic Maturation ◽  
Cdc2 Kinase ◽  
Kinase Activation ◽  
Cell Cycle Activation ◽  
Map Kinase Phosphatase ◽  
Universal Mechanism

MAP kinase activation occurs during meiotic maturation of oocytes from all animals, but the requirement for MAP kinase activation in reinitiation of meiosis appears to vary between different classes. In particular, it has become accepted that MAP kinase activation is necessary for progesterone-stimulated meiotic maturation of Xenopus oocytes, while this is clearly not the case in other systems. In this paper, we demonstrate that MAP kinase activation in Xenopus oocytes is an early response to progesterone and can be temporally dissociated from MPF activation. We show that MAP kinase activation can be suppressed by treatment with geldanamycin or by overexpression of the MAP kinase phosphatase Pyst1. A transient and low-level early activation of MAP kinase increases the efficiency of cell cycle activation later on, when MAP kinase activity is no longer essential. Many oocytes can still undergo reinitiation of meiosis in the absence of active MAP kinase. Suppression of MAP kinase activation does not affect the formation or activation of Cdc2-cyclin B complexes, but reduces the level of active Cdc2 kinase. We discuss these findings in the context of a universal mechanism for meiotic maturation in oocytes throughout the animal kingdom.

scholarly journals Okadaic acid mimics a nuclear component required for cyclin B-cdc2 kinase microinjection to drive starfish oocytes into M phase.

1991 ◽  
Vol 115 (2) ◽  
pp. 337-344 ◽  
Author(s):  
A Picard ◽  
J C Labbé ◽  
H Barakat ◽  
J C Cavadore ◽  
M Dorée
Keyword(s):  
Okadaic Acid ◽  
Xenopus Oocytes ◽  
Cyclin B ◽  
G2 Arrest ◽  
Cdc2 Kinase ◽  
Nuclear Envelope Breakdown ◽  
M Phase ◽  
Nuclear Component ◽  
Amplification Loop ◽  
Do So

G2-arrested oocytes contain cdc2 kinase as an inactive cyclin B-cdc2 complex. When a small amount of highly purified and active cdc2 kinase, prepared from starfish oocytes at first meiotic metaphase, is microinjected into Xenopus oocytes, it induces activation of the inactive endogenous complex and, as a consequence, drives the recipient oocytes into M phase. In contrast, the microinjected kinase undergoes rapid inactivation in starfish oocytes, which remain arrested at G2. Endogenous cdc2 kinase becomes activated in both nucleated and enucleated starfish oocytes injected with cytoplasm taken from maturing oocytes at the time of nuclear envelope breakdown, but only cytoplasm taken from nucleated oocytes becomes able thereafter to release second recipient oocytes from G2 arrest, and thus contains M phase-promoting factor (MPF) activity. Both nucleated and enucleated starfish oocytes produce MPF activity when type 2A phosphatase is blocked by okadaic acid. If type 2A phosphatase is only partially inhibited, neither nucleated nor enucleated oocytes produce MPF activity, although both do so if purified cdc2 kinase is subsequently injected as a primer to activate the endogenous kinase. The nucleus of starfish oocytes contains an inhibitor of type 2A phosphatase, but neither active nor inactive cdc2 kinase. Microinjection of the content of a nucleus into the cytoplasm of G2-arrested starfish oocytes activates endogenous cdc2 kinase, produces MPF activity, and drives the recipient oocytes into M phase. Together, these results show that the MPF amplification loop is controlled, both positively and negatively, by cdc2 kinase and type 2A phosphatase, respectively. Activation of the MPF amplification loop in starfish requires a nuclear component to inhibit type 2A phosphatase in cytoplasm.

scholarly journals Identification of an activator required for elevation of maturation-promoting factor (MPF) activity by gamma-S-ATP.

1990 ◽  
Vol 110 (5) ◽  
pp. 1583-1588 ◽  
Author(s):  
S Yamashita ◽  
J L Maller
Keyword(s):  
Cell Cycle ◽  
Protein Kinase ◽  
Cell Cycle Control ◽  
Control Element ◽  
Kinase Activation ◽  
Cell Extracts ◽  
M Phase ◽  
A Cell ◽  
Gamma S ◽  
Maturation Promoting Factor

Maturation-promoting factor (MPF) is a cell cycle control element able to cause cells to enter M-phase upon microinjection and will induce metaphase in nuclei incubated in cell extracts. Previous work has shown that MPF is composed of a complex between p34cdc 2 protein kinase and a B-type cyclin. In the present work gamma-S-ATP was found to cause activation of MPF activity in partially purified preparations, but this activation was lost upon chromatography on Matrex Green gel A. Readdition of other Matrex Green fractions to purified MPF restored the ability of gamma-S-ATP to activate MPF for nuclear breakdown as well as phosphorylation of histone H1. Use of the system described here will facilitate study of p34cdc 2 kinase activation and identification of elements involved in MPF regulation.

An okadaic acid-sensitive phosphatase negatively controls the cyclin degradation pathway in amphibian eggs

1991 ◽  
Vol 11 (2) ◽  
pp. 1171-1175
Author(s):  
T Lorca ◽  
D Fesquet ◽  
F Zindy ◽  
F Le Bouffant ◽  
M Cerruti ◽  
...  
Keyword(s):  
Okadaic Acid ◽  
Protease Activity ◽  
Degradation Pathway ◽  
Meiotic Metaphase ◽  
Factor Activity ◽  
Cdc2 Kinase ◽  
Phosphatase Inhibitor ◽  
M Phase ◽  
Maturation Promoting Factor

Inhibition of okadaic acid-sensitive phosphatases released the cyclin degradation pathway from its inhibited state in extracts prepared from unfertilized Xenopus eggs arrested at the second meiotic metaphase. It also switched on cyclin protease activity in a permanent fashion in interphase extracts prepared from activated eggs. Even after cdc2 kinase inactivation, microinjection of okadaic acid-treated interphase extracts pushed G2-arrested recipient oocytes into the M phase, suggesting that the phosphatase inhibitor stabilizes the activity of an unidentified factor which shares in common with cdc2 kinase the maturation-promoting factor activity.

Active cyclin B-cdc2 kinase does not inhibit DNA replication and cannot drive prematurely fertilized sea urchin eggs into mitosis

1995 ◽  
Vol 108 (7) ◽  
pp. 2693-2703 ◽  
Author(s):  
A.M. Geneviere-Garrigues ◽  
A. Barakat ◽  
M. Doree ◽  
J.L. Moreau ◽  
A. Picard
Keyword(s):  
Dna Replication ◽  
Sea Urchin ◽  
S Phase ◽  
Cyclin B ◽  
G1 Arrest ◽  
Cdc2 Kinase ◽  
Kinase Activation ◽  
M Phase ◽  
Set Up ◽  
The One

Feedback mechanisms preventing M phase occurrence before S phase completion are assumed to depend on inhibition of cyclin B-cdc2 kinase activation by unreplicated DNA. In sea urchin, fertilization stimulates protein synthesis and releases eggs from G1 arrest. We found that in the one-cell sea urchin embryo cyclin B-cdc2 kinase undergoes partial activation before S phase, reaching in S phase a level that is sufficient for G2-M phase transition. S phase entry is not inhibited by this level of cyclin B-dependent kinase activity. Inhibition of DNA replication by aphidicolin suppresses nuclear envelope breakdown, yet it does not prevent the microtubule array from being converted from its interphasic to its mitotic state. Moreover, mitotic cytoplasmic events occur at the same time in control and aphidicolin-treated embryos. Thus unreplicated DNA only prevents mitotic nuclear, not cytoplasmic, events from occurring prematurely. These results together show that the inhibition of cyclin B-cdc2 kinase activation is probably not the only mechanism that prevents mitotic nuclear events from occurring as long as DNA replication has not been completed. In contrast, cytoplasmic mitotic events seem to be controlled by a timing mechanism independent of DNA replication, set up at fertilization, that prevents premature opening of a window for mitotic events.

scholarly journals An okadaic acid-sensitive phosphatase negatively controls the cyclin degradation pathway in amphibian eggs.

1991 ◽  
Vol 11 (2) ◽  
pp. 1171-1175 ◽  
Author(s):  
T Lorca ◽  
D Fesquet ◽  
F Zindy ◽  
F Le Bouffant ◽  
M Cerruti ◽  
...  
Keyword(s):  
Okadaic Acid ◽  
Protease Activity ◽  
Degradation Pathway ◽  
Meiotic Metaphase ◽  
Factor Activity ◽  
Cdc2 Kinase ◽  
Phosphatase Inhibitor ◽  
M Phase ◽  
Maturation Promoting Factor

Inhibition of okadaic acid-sensitive phosphatases released the cyclin degradation pathway from its inhibited state in extracts prepared from unfertilized Xenopus eggs arrested at the second meiotic metaphase. It also switched on cyclin protease activity in a permanent fashion in interphase extracts prepared from activated eggs. Even after cdc2 kinase inactivation, microinjection of okadaic acid-treated interphase extracts pushed G2-arrested recipient oocytes into the M phase, suggesting that the phosphatase inhibitor stabilizes the activity of an unidentified factor which shares in common with cdc2 kinase the maturation-promoting factor activity.

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