The natural arrest of vertebrate unfertilized eggs in second meiotic metaphase results from the activity cytostatic factor (CSF). product c-mosxe proto-oncogene is thought to be a component CSF and can induce when injected into blastomeres two-cell embryos. c-Mosxe protein directly activate mitogen-activated kinase (MAP kinase) vitro, leading activation MAP kinase. are active rapidly inactivated after fertilization. Microinjection thiophosphorylated one blastomere embryo induced similar that...

ABSTRACT The tyrosine phosphorylation/dephosphorylation of p34cdc2 was estimated by immunoblotting with antiphosphotyrosine antibody during meiotic maturation Xenopus oocytes. At the time germinal vesicle breakdown (GVBD), is dephosphorylated whereas a p42 protein, which might correspond to MAP2 kinase, becomes phosphorylated. No modification in level phosphorylation either proteins noticed whole process from GVBD until metaphase H. When added prophase oocytes, 6-DMAP...

Abstract Large vertebrate genomes duplicate by activating tens of thousands DNA replication origins, irregularly spaced along the genome. The spatial and temporal regulation process is not yet fully understood. To investigate dynamics, we developed a methodology called RepliCorr, which uses correlation between patterns observed on stretched single-molecule obtained either combing or high-throughput optical mapping. analysis revealed two independent spatiotemporal processes that regulate...

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 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...

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...

Abstract The activation of eukaryotic DNA replication origins needs to be strictly controlled at multiple steps in order faithfully duplicate the genome and maintain its stability. How checkpoint recovery adaptation protein Polo-like kinase 1 (Plk1) regulates firing during non-challenged S phase remained an open question. Using fiber analysis, we show that immunodepletion Plk1 Xenopus vitro system decreases fork density initiation frequency. Numerical analyses suggest reduces overall...

Vertebrate oocytes proceed through the 1st and 2nd meiotic division without intervening S-phase to become haploid. Although DNA replication does not take place, unfertilized acquire competence replicate one hour after division, by accumulating an essential factor of replicative machinery, Cdc6. Here, we discovered that turnover Cdc6 is precisely regulated in avoid inhibition Cdk1. At meiosis resumption, starts be expressed but cannot accumulate due a degradation mechanism activated During...

In multicellular eukaryotic organisms, the initiation of DNA replication occurs asynchronously throughout S-phase according to a regulated timing program. Here, using Xenopus egg extracts, we showed that Yap (Yes-associated protein 1), downstream effector Hippo signalling pathway, is required for control dynamics. We found recruited chromatin at start and identified Rif1, major regulator program, as novel binding protein. Furthermore, show either or Rif1 depletion accelerates dynamics by...

Polo-like kinase 1 (Plk1) is a cell cycle essential for mitosis progression, but also important checkpoint recovery and adaptation in response to DNA damage replication stress. However, although Plk1 expressed S phase, little known about its function during unperturbed replication. Using Xenopus laevis egg extracts, mimicking early embryonic replication, we demonstrate that simultaneously recruited chromatin with pre-replication proteins where it accumulates throughout phase. Further, found...

The small protein ARPP19 plays a dual role during oocyte meiosis resumption. In Xenopus, phosphorylation at S109 by PKA is necessary for maintaining oocytes arrested in prophase of the first meiotic division. Progesterone downregulates PKA, leading to dephosphorylation S109. This initiates transduction pathway ending with activation universal inducer M-phase, kinase Cdk1. last step depends on S67 Greatwall. Hence, phosphorylated S109, restrains Cdk1 while when Greatwall S67, becomes an...