Click here to close
Hello! We notice that you are using Internet Explorer, which is not supported by Xenbase and may cause the site to display incorrectly.
We suggest using a current version of Chrome,
FireFox, or Safari.
A developmental timer regulates degradation of cyclin E1 at the midblastula transition during Xenopus embryogenesis.
Howe JA
,
Newport JW
.
???displayArticle.abstract???
We have analyzed cyclin E1, a protein that is essential for the G1/S transition, during early development in Xenopus embryos. Cyclin E1 was found to be abundant in eggs, and after fertilization, until the midblastula transition (MBT) when levels of cyclin E1 protein, and associated kinase activity, were found to decline precipitously. Our results suggest that the reduced level of the cyclin E1 protein detected after the MBT does not occur indirectly as a result of degradation of the maternally encoded cyclin E1 mRNA. Instead, the stability of cyclin E1 protein appears to play a major role in reduction of cyclin E1 levels at this time. Cyclin E1 protein was found to be stable during the cleavage divisions but degraded with a much shorter half-life after the MBT. Activation of cyclin E1 protein turnover occurs independent of cell cycle progression, does not require ongoing protein synthesis, and is not triggered as a result of the ratio of nuclei to cytoplasm in embryonic cells that initiates the MBT. We therefore propose that a developmental timing mechanism measures an approximately 5-hr time period, from the time of fertilization, and then allows activation of a protein degradative pathway that regulates cyclin E1. Characterization of the timer suggests that it might be held inactive in eggs by a mitogen-activated protein kinase signal transduction pathway.
Blow,
A cdc2-like protein is involved in the initiation of DNA replication in Xenopus egg extracts.
1990, Pubmed,
Xenbase
Blow,
A cdc2-like protein is involved in the initiation of DNA replication in Xenopus egg extracts.
1990,
Pubmed
,
Xenbase
Dasso,
Completion of DNA replication is monitored by a feedback system that controls the initiation of mitosis in vitro: studies in Xenopus.
1990,
Pubmed
,
Xenbase
Desai,
Activation of human cyclin-dependent kinases in vitro.
1992,
Pubmed
Dulić,
Association of human cyclin E with a periodic G1-S phase protein kinase.
1992,
Pubmed
Dunphy,
Fission yeast p13 blocks mitotic activation and tyrosine dephosphorylation of the Xenopus cdc2 protein kinase.
1989,
Pubmed
,
Xenbase
Fang,
Evidence that the G1-S and G2-M transitions are controlled by different cdc2 proteins in higher eukaryotes.
1991,
Pubmed
,
Xenbase
Girard,
Cyclin A is required for the onset of DNA replication in mammalian fibroblasts.
1991,
Pubmed
Guadagno,
A link between cyclin A expression and adhesion-dependent cell cycle progression.
1993,
Pubmed
Haccard,
Induction of metaphase arrest in cleaving Xenopus embryos by MAP kinase.
1993,
Pubmed
,
Xenbase
Howe,
Identification of a developmental timer regulating the stability of embryonic cyclin A and a new somatic A-type cyclin at gastrulation.
1995,
Pubmed
,
Xenbase
Kimelman,
The events of the midblastula transition in Xenopus are regulated by changes in the cell cycle.
1987,
Pubmed
,
Xenbase
King,
Mitosis in transition.
1994,
Pubmed
Knoblich,
Cyclin E controls S phase progression and its down-regulation during Drosophila embryogenesis is required for the arrest of cell proliferation.
1994,
Pubmed
Koff,
Formation and activation of a cyclin E-cdk2 complex during the G1 phase of the human cell cycle.
1992,
Pubmed
Lew,
Isolation of three novel human cyclins by rescue of G1 cyclin (Cln) function in yeast.
1991,
Pubmed
Mansour,
Transformation of mammalian cells by constitutively active MAP kinase kinase.
1994,
Pubmed
Nebreda,
The c-mos proto-oncogene protein kinase turns on and maintains the activity of MAP kinase, but not MPF, in cell-free extracts of Xenopus oocytes and eggs.
1993,
Pubmed
,
Xenbase
Newport,
A major developmental transition in early Xenopus embryos: I. characterization and timing of cellular changes at the midblastula stage.
1982,
Pubmed
,
Xenbase
Newport,
Regulation of the cell cycle during early Xenopus development.
1984,
Pubmed
,
Xenbase
Newport,
On the coupling between DNA replication and mitosis.
1989,
Pubmed
,
Xenbase
Newport,
A major developmental transition in early Xenopus embryos: II. Control of the onset of transcription.
1982,
Pubmed
,
Xenbase
Ohtsubo,
Cyclin-dependent regulation of G1 in mammalian fibroblasts.
1993,
Pubmed
Ohtsubo,
Human cyclin E, a nuclear protein essential for the G1-to-S phase transition.
1995,
Pubmed
Pagano,
Cyclin A is required at two points in the human cell cycle.
1992,
Pubmed
Peng,
Xenopus laevis: Practical uses in cell and molecular biology. Solutions and protocols.
1991,
Pubmed
,
Xenbase
Rempel,
Maternal Xenopus Cdk2-cyclin E complexes function during meiotic and early embryonic cell cycles that lack a G1 phase.
1995,
Pubmed
,
Xenbase
Resnitzky,
Acceleration of the G1/S phase transition by expression of cyclins D1 and E with an inducible system.
1994,
Pubmed
Sagata,
The c-mos proto-oncogene product is a cytostatic factor responsible for meiotic arrest in vertebrate eggs.
1989,
Pubmed
,
Xenbase
Sagata,
Function of c-mos proto-oncogene product in meiotic maturation in Xenopus oocytes.
1988,
Pubmed
,
Xenbase
Sherr,
G1 phase progression: cycling on cue.
1994,
Pubmed
Shibuya,
Mos induces the in vitro activation of mitogen-activated protein kinases in lysates of frog oocytes and mammalian somatic cells.
1993,
Pubmed
,
Xenbase
Tsai,
Isolation of the human cdk2 gene that encodes the cyclin A- and adenovirus E1A-associated p33 kinase.
1991,
Pubmed
,
Xenbase
Watanabe,
Specific proteolysis of the c-mos proto-oncogene product by calpain on fertilization of Xenopus eggs.
1989,
Pubmed
,
Xenbase
Wimmel,
Inducible acceleration of G1 progression through tetracycline-regulated expression of human cyclin E.
1994,
Pubmed
Yew,
Meiotic initiation by the mos protein in Xenopus.
1992,
Pubmed
,
Xenbase
