Cyclin E and its associated cdk activity do not cycle during early embryogenesis of the sea Urchin.
Dev Biol
; 234(2): 425-40, 2001 Jun 15.
Article
en En
| MEDLINE
| ID: mdl-11397011
ABSTRACT
Female sea urchins store their gametes as haploid eggs. The zygote enters S-phase 1 h after fertilization, initiating a series of cell cycles that lack gap phases. We have cloned cyclin E from the sea urchin Strongylocentrotus purpuratus. Cyclin E is synthesized during oogenesis, is present in the germinal vesicle, and is released into the egg cytoplasm at oocyte maturation. Cyclin E synthesis is activated at fertilization, although there is no increase in cyclin E protein levels due to continuous turnover of the protein. Cyclin E protein levels decline in morula embryos, while cyclin E mRNA levels remain high. After the blastula stage, cyclin E mRNA and protein levels are very low, and cyclin E expression is predominant only in cells that are actively dividing. These include cells in the left coelomic pouch, which forms the adult rudiment in the embryo. The cyclin E present in the egg is complexed with a protein kinase. Activity of the cyclin E/cdk2 changes little during the initial cell cycles. In particular, cyclin E-cdk2 levels remain high during both S-phase and mitosis. Our results suggest that progression through the early embryonic cell cycles in the sea urchin does not require fluctuations in cyclin E kinase activity.
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Colección:
01-internacional
Base de datos:
MEDLINE
Asunto principal:
Erizos de Mar
/
Proteínas Serina-Treonina Quinasas
/
Quinasas Ciclina-Dependientes
/
Ciclina E
/
Quinasas CDC2-CDC28
Tipo de estudio:
Risk_factors_studies
Límite:
Animals
Idioma:
En
Revista:
Dev Biol
Año:
2001
Tipo del documento:
Article
País de afiliación:
Estados Unidos