Cyclin B mRNA depletion only transiently inhibits the Xenopus embryonic cell cycle

Development ◽  
1991 ◽  
Vol 111 (4) ◽  
pp. 1173-1178 ◽  
Author(s):  
D.L. Weeks ◽  
J.A. Walder ◽  
J.M. Dagle
Keyword(s):  
Cell Cycle ◽  
Cell Division ◽  
Antisense Oligonucleotides ◽  
Normal Development ◽  
Embryonic Cell ◽  
Cyclin B ◽  
Xenopus Embryos ◽  
Embryonic Cleavage ◽  
Embryonic Cell Cycle

The control of the cell cycle is dependent on the ability to synthesize and degrade proteins called cyclins. When antisense oligonucleotides are used to deplete Xenopus embryos of mRNA encoding cyclin B protein, embryonic cleavage is inhibited. Surprisingly, after missing several rounds of cleavage, the cell cycle and cell division resumes. These studies indicate that the early embryonic cell cycle can proceed with undetectable levels of cyclin B encoding mRNA. In contrast, other events of normal development, including the activation of embryonic transcription and gastrulation, are inhibited.

The cytoskeleton-dependent localization of cdc2/cyclin B in blastomere cortex duringXenopus embryonic cell cycle

2005 ◽  
Vol 72 (3) ◽  
pp. 336-345 ◽  
Author(s):  
Norihiko Nakamura ◽  
Toshinobu Tokumoto ◽  
Shuichi Ueno ◽  
Yasuhiro Iwao
Keyword(s):  
Cell Cycle ◽  
Embryonic Cell ◽  
Cyclin B ◽  
Embryonic Cell Cycle

Association of cyclin-bound p34cdc2 with subcellular structures in xenopus eggs

1992 ◽  
Vol 102 (2) ◽  
pp. 285-297 ◽  
Author(s):  
D. Leiss ◽  
M.A. Felix ◽  
E. Karsenti
Keyword(s):  
Cell Cycle ◽  
Ribosomal Proteins ◽  
Cell Cycle Progression ◽  
Gradient Centrifugation ◽  
Preliminary Evidence ◽  
Embryonic Cell ◽  
Cytoskeletal Proteins ◽  
Cyclin B ◽  
Post Translational Modifications ◽  
Egg Extracts

Cell cycle progression is controlled by changes in kinase activity of homologs of the fission yeast protein p34cdc2. The p34cdc2 kinase is activated by its association with a cyclin subunit, followed by post-translational modifications. Here, we show that in Xenopus eggs stimulated to enter the early embryonic cell cycle by an electric shock, part of the p34cdc2 becomes associated with subcellular fractions as the eggs progress towards mitosis. This occurs as a result of cyclin accumulation because most of the B-type cyclins and some of the A-type cyclins are found in the particulate fraction. Moreover, as soon as cyclins are degraded, p34cdc2 is released in the soluble fraction. The p34cdc2-cyclin complex can be solubilised by 80 mM beta-glycerophosphate (in the standard MPF extraction buffer) or by high salt concentrations. The post-translational modifications leading to cdc2 kinase activation by cyclin occur in the insoluble form. Following fractionation of egg extracts by sucrose gradient centrifugation, the p34cdc2-cyclin B complex is found in several fractions, but especially in two discrete peaks. We present evidence that in the slow-sedimenting peak the p34cdc2-cyclin B complex is associated with the 60 S subunit of monoribosomes. It could be targeted in this fashion to substrates such as ribosomal proteins and maybe to cytoskeletal proteins, since ribosomes bind to microtubules and are present in the spindle. The p34cdc2-cyclin B complex is also found in a faster-migrating fraction containing various membranous structures, including Golgi stacks. Therefore, as observed by immunofluorescence in other systems, it seems that cyclin subunits target p34cdc2 to specific cellular sites and this is certainly important for its function. In addition, we present preliminary evidence suggesting that some component present in the ribosome-containing fraction is required for activation of the p34cdc2-cyclin B complex.

scholarly journals Intracellular free calcium oscillates during cell division of Xenopus embryos.

1991 ◽  
Vol 112 (4) ◽  
pp. 711-718 ◽  
Author(s):  
N Grandin ◽  
M Charbonneau
Keyword(s):  
Cell Cycle ◽  
Cell Division ◽  
Cell Volume ◽  
Intracellular Ph ◽  
Calcium Ions ◽  
Volume Ratio ◽  
Mean Amplitude ◽  
Free Calcium ◽  
Periodic Oscillations ◽  
Xenopus Embryos

In Xenopus embryos, previous results failed to detect changes in the activity of free calcium ions (Ca2+i) during cell division using Ca2(+)-selective microelectrodes, while experiments with aequorin yielded uncertain results complicated by the variation during cell division of the aequorin concentration to cell volume ratio. We now report, using Ca2(+)-selective microelectrodes, that cell division in Xenopus embryos is accompanied by periodic oscillations of the Ca2+i level, which occur with a periodicity of 30 min, equal to that of the cell cycle. These Ca2+i oscillations were detected in 24 out of 35 experiments, and had a mean amplitude of 70 nM, around a basal Ca2+i level of 0.40 microM. Ca2+i oscillations did not take place in the absence of cell division, either in artificially activated eggs or in cleavage-blocked embryos. Therefore, Ca2+i oscillations do not represent, unlike intracellular pH oscillations (Grandin, N., and M. Charbonneau. J. Cell Biol. 111:523-532. 1990), a component of the basic cell cycle ("cytoplasmic clock" or "master oscillator"), but appear to be more likely related to some events of mitosis.

Overexpression of a truncated cyclin B gene arrests Dictyostelium cell division during mitosis

1994 ◽  
Vol 107 (11) ◽  
pp. 3105-3114 ◽  
Author(s):  
Q. Luo ◽  
C. Michaelis ◽  
G. Weeks
Keyword(s):  
Cell Cycle ◽  
Cell Division ◽  
Cell Growth ◽  
Dictyostelium Discoideum ◽  
Single Copy ◽  
Cyclin B ◽  
Dictyostelium Cell ◽  
Maximum Accumulation ◽  
Sequence Identity ◽  
Cyclin Gene

A cyclin gene has been isolated from Dictyostelium discoideum and the available evidence indicates that the gene encodes a B type cyclin. The cyclin box region of the protein encoded by the gene, clb1, has the highest degree of sequence identity with the B-type cyclins of other species. Levels of cyclin B mRNA and protein oscillate during the cell cycle with maximum accumulation of mRNA occurring prior to cell division and maximum levels of protein occurring during cell division. Overexpression of a N-terminally truncated cyclin B protein lacking the destruction box inhibits cell growth by arresting cell division during mitosis. The gene is present as a single copy in the Dictyostelium genome and there is no evidence for any other highly related cyclin B genes.

Subcellular localisation of human wee1 kinase is regulated during the cell cycle

1995 ◽  
Vol 108 (6) ◽  
pp. 2425-2432
Author(s):  
V. Baldin ◽  
B. Ducommun
Keyword(s):  
Cell Cycle ◽  
Cell Division ◽  
Tyrosine Phosphatase ◽  
Cyclin B ◽  
Microtubule Assembly ◽  
Subcellular Localisation ◽  
Temporal Regulation ◽  
Wee1 Kinase ◽  
Cdc2 Activity ◽  
Intracellular Localisation

Wee1 kinase-dependent phosphorylation of cdc2 maintains the cdc2/cyclin B complex in an inert form until it is activated by the cdc25 tyrosine phosphatase at the end of G2. As described for cdc25, cell cycle-linked changes in the intracellular localisation of wee1 may constitute an important aspect of the temporal regulation of cdc2 activity. Here we report that the subcellular distribution of human wee1 changes during the cell cycle in HeLa and IMR90 cells. During interphase, wee1 is found almost exclusively in the nucleus. When the cell enters mitosis, wee1 is relocalised into the cytoplasm. During cell division, wee1 becomes restricted to the mitotic equator and by the end of mitosis it is found exclusively in association with midbody bridges, a phenomenon that is dependent on microtubule assembly. The relocalisations of wee1 and its association with subcellular structures may play key regulatory roles at different stages of the cell cycle and during mitosis.

scholarly journals Accumulation and dynamics of proteins of the MCM family during mouse oogenesis and the first embryonic cell cycle

2007 ◽  
Vol 51 (4) ◽  
pp. 283-295 ◽  
Author(s):  
Lukasz Swiech ◽  
Katarzyna Kisiel ◽  
Renata Czolowska ◽  
Maciej Zientarski ◽  
Ewa Borsuk
Keyword(s):  
Cell Cycle ◽  
Embryonic Cell ◽  
Embryonic Cell Cycle

scholarly journals A Role for Cdk2 Kinase in Negatively Regulating DNA Replication during S Phase of the Cell Cycle

1997 ◽  
Vol 137 (1) ◽  
pp. 183-192 ◽  
Author(s):  
Xuequn Helen Hua ◽  
Hong Yan ◽  
John Newport
Keyword(s):  
Cell Cycle ◽  
Dna Replication ◽  
Cyclin E ◽  
Embryonic Cell ◽  
S Phase ◽  
Negative Regulation ◽  
Sperm Chromatin ◽  
High Concentration ◽  
Low Concentrations ◽  
Embryonic Cell Cycle

Using cell-free extracts made from Xenopus eggs, we show that cdk2-cyclin E and A kinases play an important role in negatively regulating DNA replication. Specifically, we demonstrate that the cdk2 kinase concentration surrounding chromatin in extracts increases 200-fold once the chromatin is assembled into nuclei. Further, we find that if the cdk2–cyclin E or A concentration in egg cytosol is increased 16-fold before the addition of sperm chromatin, the chromatin fails to initiate DNA replication once assembled into nuclei. This demonstrates that cdk2–cyclin E or A can negatively regulate DNA replication. With respect to how this negative regulation occurs, we show that high levels of cdk2–cyclin E do not block the association of the protein complex ORC with sperm chromatin but do prevent association of MCM3, a protein essential for replication. Importantly, we find that MCM3 that is prebound to chromatin does not dissociate when cdk2– cyclin E levels are increased. Taken together our results strongly suggest that during the embryonic cell cycle, the low concentrations of cdk2–cyclin E present in the cytosol after mitosis and before nuclear formation allow proteins essential for potentiating DNA replication to bind to chromatin, and that the high concentration of cdk2–cyclin E within nuclei prevents MCM from reassociating with chromatin after replication. This situation could serve, in part, to limit DNA replication to a single round per cell cycle.

scholarly journals The Design Space of the Embryonic Cell Cycle Oscillator

2017 ◽  
Vol 113 (3) ◽  
pp. 743-752 ◽  
Author(s):  
Henry H. Mattingly ◽  
Moshe Sheintuch ◽  
Stanislav Y. Shvartsman
Keyword(s):  
Cell Cycle ◽  
Design Space ◽  
Embryonic Cell ◽  
Embryonic Cell Cycle
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