The Ras and Raf1 proto-oncogenes transduce extracellular signals that promote cell growth. Cdc25 phosphatases activate the division cycle by dephosphorylation of critical threonine tyrosine residues within cyclin-dependent kinases. We show here phosphatase associates with raf1 in somatic mammalian cells meiotic frog oocytes. Furthermore, can be activated vitro a Raf1-dependent manner. suggest activation Ras/Raf1 pathways might mediated part Cdc25.

O-Linked N-acetylglucosaminylation (O-GlcNAcylation) (or O-linked N-acetylglucosamine (O-GlcNAc)) is an abundant and reversible glycosylation type found within the cytosolic nuclear compartments. We have described previously sudden O-GlcNAcylation increase occurring during Xenopus laevis oocyte G2/M transition, we demonstrated that inhibition of O-GlcNAc-transferase (OGT) blocked this process, showing dynamism interferes with cell cycle progression. In work, identified proteins are...

Cyclin-dependent kinases (Cdks) are key regulators of the eukaryotic cell division cycle. Cdk1 (Cdc2) and Cdk2 should be bound to regulatory subunits named cyclins as well phosphorylated on a conserved Thr located in T-loop for full enzymatic activity. Cdc2- Cdk2-cyclin complexes can inactivated by phosphorylation catalytic cleft-located Thr-14 Tyr-15 residues or association with inhibitory such p21Cip1. We have recently identified novel Cdc2 regulator RINGO that plays an important role...

ABSTRACT The auto-catalytic activation of the cyclin-dependent kinase Cdc2 or MPF (M-phase promoting factor) is an irreversible process responsible for entry into M phase. In Xenopus oocyte, a positive feed-back loop between and its activating phosphatase Cdc25 allows abrupt first meiotic division. We have studied Cdc2/Cdc25 using cell-free systems derived from prophase-arrested oocyte. Our findings support following two-step model amplification: during step, acquires basal catalytic...

Progesterone-induced meiotic maturation of Xenopusoocytes requires the synthesis new proteins, such as Mos and cyclin B. Synthesis is thought to be necessary sufficient for maturation; however, it has recently been proposed that newly synthesized proteins binding p34 cdc2 could involved in a signaling pathway triggers activation maturation-promoting factor. We focused our attention on B because they are response progesterone, bind , their microinjection into resting oocytes induces...

We previously reported that immunodepletion of Greatwall kinase prevents Xenopus egg extracts from entering or maintaining M phase due to the accumulation inhibitory phosphorylations on Thr14 and Tyr15 Cdc2. phase–promoting factor (MPF) in turn activates Greatwall, implying participates an MPF autoregulatory loop. show here activated both accelerates mitotic G2/M transition cycling induces meiotic maturation G2-arrested oocytes absence progesterone. Activated can induce Cdc25 activity Cdc2,...

ABSTRACT The total level of tubulin and the ratio polymeric to dimer were measured by a colchicine filter-binding assay during meiotic maturation Xenopus oocyte. Although remains unchanged (0·12 ± 0·03 μg/oocyte), decreases (25% in prophase oocytes versus 20% metaphase oocytes). percentage polymerized was estimated after drug (nocodazole taxol) treatments cold treatment progesterone-matured oocytes; all cases microtubules present mature oocyte are less stable than microtubules. presence...

Fully grown Xenopus oocyte is arrested at prophase I of meiosis. Re-entry into meiosis depends on the activation MPF (M-phase promoting factor or cyclin B.Cdc2 complex), triggered by progesterone. The prophase-arrested contains a store Cdc2. Most protein present as monomer whereas minor fraction, called pre-MPF, found to be associated with B. Activation Cdc2 two key events: binding and an activating phosphorylation Thr-161 residue located in T-loop. To get new insights regulation Cdc2,...

ABSTRACT Xenopusprophase oocytes reenter meiotic division in response to progesterone. The signaling pathway leading Cdc2 activation depends on neosynthesized proteins and a decrease PKA activity. We demonstrate that Eg2 protein, Xenopusmember of the Aurora/Ipl1 family protein kinases, accumulates progesterone is degraded after parthenogenetic activation. polyadenylation cap ribose methylation mRNA are not needed for accumulation. accumulation induced by through activity, upstream kinase...

We have characterized a serine/threonine protein kinase from Xenopus metaphase‐II‐blocked oocytes, which phosphorylates in vitro the microtubule‐associated 2 (MAP2). The MAP2 activity, undetectable prophase is activated during progesterone‐induced meiotic maturation (G ‐M transition of cell cycle). p ‐Nitrophenyl phosphate, phosphatase inhibitor, required to prevent spontaneous deactivation crude preparations; conversely, partially purified enzyme can be deactiyated by low‐ M r...

In many cell types, the mitogen-activated protein kinase (MAPK) also named extracellular signal-regulated (ERK) is activated in response to a variety of growth factor-receptor interactions and leads transcriptional activation immediate early genes, hereby influencing number tissue-specific biological activities, as proliferation, survival differentiation. one specific type however, female germ cell, MAPK does not follow this canonical scheme. oocytes, independently factors tyrosine...

Xenopus oocytes are arrested in meiotic prophase I and resume divisions response to progesterone. Progesterone triggers activation of M-phase promoting factor (MPF) or Cdc2-cyclin B complex neosynthesis Mos kinase, responsible for MAPK activation. Both Cdc2 activities required the success maturation. However, signaling pathway induced by progesterone leading MPF is poorly understood, most targets both oocyte remain be determined. Aurora-A a Ser/Thr kinase involved separation centrosomes...

In fully grown oocytes, meiosis is arrested at first prophase until species-specific initiation signals trigger maturation. Meiotic resumption universally involves early activation of M phase-promoting factor (Cdc2 kinase-Cyclin B complex, MPF) by dephosphorylation the inhibitory Thr14/Tyr15 sites Cdc2. However, underlying mechanisms vary. Xenopus deciphering intervening chain events has been hampered a sensitive amplification loop involving Cdc2-Cyclin B, kinase Myt1 and activating...

Ovulated eggs possess maternal apoptotic execution machinery that is inhibited for a limited time. The fertilized switch off this time bomb whereas aged unfertilized and parthenogenetically activated fail to stop the timer die. To investigate nature of molecular clock triggers egg decision committing suicide, we introduce here Xenopus as an in vivo system studying death eggs. We report after ovulation, number remains female body where they die by apoptosis. Similarly, ovulated recovered...

Entry into mitosis or meiosis relies on the coordinated action of kinases and phosphatases that ultimately leads to activation Cyclin B-Cdk1, also called MPF for M-phase promoting factor. Vertebrate oocytes are blocked in prophase first meiotic division, an arrest tightly controlled by a high PKA activity. Reentry depends Cdk1 obeys two steps mechanism: catalytic amount is generated protein synthesis-dependent manner; then regulatory network auto-amplification loop initiated. This second...