Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 7 de 7
Filtrar
Mais filtros










Base de dados
Intervalo de ano de publicação
1.
Trends Genet ; 32(8): 496-507, 2016 08.
Artigo em Inglês | MEDLINE | ID: mdl-27339317

RESUMO

At the mid-blastula transition (MBT), externally developing embryos refocus from increasing cell number to elaboration of the body plan. Studies in Drosophila reveal a sequence of changes in regulators of Cyclin:Cdk1 that increasingly restricts the activity of this cell cycle kinase to slow cell cycles during early embryogenesis. By reviewing these events, we provide an outline of the mechanisms slowing the cell cycle at and around the time of MBT. The perspectives developed should provide a guiding paradigm for the study of other MBT changes as the embryo transits from maternal control to a regulatory program centered on the expression of zygotic genes.


Assuntos
Proteína Quinase CDC2/genética , Ciclinas/genética , Desenvolvimento Embrionário/genética , Regulação da Expressão Gênica no Desenvolvimento/genética , Animais , Blástula/crescimento & desenvolvimento , Ciclo Celular/genética , Drosophila/genética , Drosophila/crescimento & desenvolvimento , Proteínas de Drosophila
3.
Genes Dev ; 26(7): 714-25, 2012 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-22431511

RESUMO

The Drosophila midblastula transition (MBT), a major event in embryogenesis, remodels and slows the cell cycle. In the pre-MBT cycles, all genomic regions replicate simultaneously in rapid S phases that alternate with mitosis, skipping gap phases. At the MBT, down-regulation of Cdc25 phosphatase and the resulting inhibitory phosphorylation of the mitotic kinase Cdk1 create a G2 pause in interphase 14. However, an earlier change in interphase 14 is the prolongation of S phase. While the signals modifying S phase are unknown, the onset of late replication-where replication of constitutively heterochromatic satellite sequences is delayed-extends S-phase 14. We injected Cdc25 mRNA to bypass the developmentally programmed down-regulation of Cdc25 at the MBT. Introduction of either Cdc25 isoform (String or Twine) or enhanced Cdk1 activity triggered premature replication of late-replicating sequences, even after their specification, and thereby shortened S phase. Reciprocally, reduction of Cdk1 activity by knockdown of mitotic cyclins extended pre-MBT S phase. These findings suggest that high Cdc25 and Cdk1 contribute to the speed of the rapid, pre-MBT S phases and that down-regulation of these activities plays a broader role in MBT-associated changes than was previously suspected.


Assuntos
Replicação do DNA , DNA/metabolismo , Drosophila melanogaster/embriologia , Drosophila melanogaster/enzimologia , Regulação da Expressão Gênica no Desenvolvimento , Fosfatases cdc25/metabolismo , Animais , Proteína Quinase CDC2/metabolismo , Regulação para Baixo , Drosophila melanogaster/citologia , Drosophila melanogaster/genética , Mitose , Fase S , Fosfatases cdc25/genética
4.
Curr Biol ; 20(23): 2067-77, 2010 Dec 07.
Artigo em Inglês | MEDLINE | ID: mdl-21074439

RESUMO

BACKGROUND: Fast, early embryonic cell cycles have correspondingly fast S phases. In early Drosophila embryos, forks starting from closely spaced origins replicate the whole genome in 3.4 min, ten times faster than in embryonic cycle 14 and a hundred times faster than in a wing disc. It is not known how S phase duration is regulated. Here we examined prolongation of embryonic S phases, its coupling to development, and its relationship to the appearance of heterochromatin. RESULTS: Imaging of fluorescent nucleotide incorporation and GFP-PCNA gave exquisite time resolution of S phase events. In the early S phases, satellite sequences replicated rapidly despite a compact chromatin structure. In S phases 11-13, a delay in satellite replication emerged in sync with modest and progressive prolongation of S phase. In S phase 14, major and distinct delays ordered the replication of satellites into a sequence that occupied much of S phase. This onset of late replication required transcription. Satellites only accumulated abundant heterochromatin protein 1 (HP1) after replicating in S phase 14. By cycle 15, satellites clustered in a compact HP1-positive mass, but replication occurred at decondensed foci at the surface of this mass. CONCLUSIONS: The slowing of S phase is an active process, not a titration of maternal replication machinery. Most sequences continue to replicate rapidly in successive cycles, but increasing delays in the replication of satellite sequences extend S phase. Although called constitutively heterochromatic, satellites acquire the distinctive features of heterochromatin, compaction, late replication, HP1 binding, and aggregation at the chromocenter, in successive steps coordinated with developmental progress.


Assuntos
Replicação do DNA , Drosophila melanogaster/embriologia , Drosophila melanogaster/genética , Fase S , Animais , Proteínas Cromossômicas não Histona/genética , Proteínas Cromossômicas não Histona/metabolismo , DNA Satélite/genética , DNA Satélite/metabolismo , Proteínas de Drosophila/genética , Proteínas de Drosophila/metabolismo , Heterocromatina/metabolismo , Antígeno Nuclear de Célula em Proliferação/genética , Antígeno Nuclear de Célula em Proliferação/metabolismo , Proteínas Recombinantes de Fusão/genética , Proteínas Recombinantes de Fusão/metabolismo
5.
J Cell Biol ; 187(1): 7-14, 2009 Oct 05.
Artigo em Inglês | MEDLINE | ID: mdl-19786576

RESUMO

We examined the contribution of S phase in timing cell cycle progression during Drosophila embryogenesis using an approach that deletes S phase rather than arresting its progress. Injection of Drosophila Geminin, an inhibitor of replication licensing, prevented subsequent replication so that the following mitosis occurred with uninemic chromosomes, which failed to align. The effect of S phase deletion on interphase length changed with development. During the maternally regulated syncytial blastoderm cycles, deleting S phase shortened interphase, and deletion of the last of blastoderm S phase (cycle 14) induced an extra synchronous division and temporarily deferred mid-blastula transition (MBT) events. In contrast, deleting S phase after the MBT in cycle 15 did not dramatically affect mitotic timing, which appears to retain its dependence on developmentally programmed zygotic transcription. We conclude that normal S phase and replication checkpoint activities are important timers of the undisturbed cell cycle before, but not after, the MBT.


Assuntos
Blástula/metabolismo , Ciclo Celular/genética , Replicação do DNA , Drosophila/embriologia , Drosophila/metabolismo , Animais , Proteínas de Ciclo Celular/metabolismo , Drosophila/genética , Proteínas de Drosophila/metabolismo , Embrião não Mamífero/citologia , Embrião não Mamífero/metabolismo , Geminina , Genes de Insetos , Fase S
6.
CSH Protoc ; 2008: pdb.ip57, 2008 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-21356900

RESUMO

INTRODUCTIONThe key consideration in preparation of baskets for Drosophila embryo collection is basket size, since the collected embryos must be in approximately one monolayer (or more). This article describes two baskets (homemade and commercial) used by the author for large numbers of embryos.

7.
Curr Biol ; 12(10): 829-33, 2002 May 14.
Artigo em Inglês | MEDLINE | ID: mdl-12015119

RESUMO

When mitosis is bypassed, as in some cancer cells or in natural endocycles, sister chromosomes remain paired and produce four-stranded diplochromosomes or polytene chromosomes. Cyclin/Cdk1 inactivation blocks entry into mitosis and can reset G2 cells to G1, allowing another round of replication. Reciprocally, persistent expression of Cyclin A/Cdk1 or Cyclin E/Cdk2 blocks Drosophila endocycles. Inactivation of Cyclin A/Cdk1 by mutation or overexpression of the Cyclin/Cdk1 inhibitor, Roughex (Rux), converts the 16(th) embryonic mitotic cycle to an endocycle; however, we show that Rux expression fails to convert earlier cell cycles unless Cyclin E is also downregulated. Following induction of a Rux transgene in Cyclin E mutant embryos during G2 of cell cycle 14 (G2(14)), Cyclins A, B, and B3 disappeared and cells reentered S phase. This rereplication produced diplochromosomes that segregated abnormally at a subsequent mitosis. Thus, like the yeast CKIs Rum1 and Sic1, Drosophila Rux can reset G2 cells to G1. The observed cyclin destruction suggests that cell cycle resetting by Rux was associated with activation of the anaphase-promoting complex (APC), while the presence of diplochromosomes implies that this activation of APC outside of mitosis was not sufficient to trigger sister disjunction.


Assuntos
Cromátides/metabolismo , Segregação de Cromossomos , Replicação do DNA , Proteínas de Drosophila , Drosophila/citologia , Drosophila/embriologia , Animais , Ciclo Celular , Cromátides/genética , Ciclina A/metabolismo , Ciclina B/metabolismo , Ciclina E/genética , Ciclina E/metabolismo , Regulação para Baixo , Drosophila/genética , Proteínas do Olho/metabolismo , Hibridização in Situ Fluorescente , Mitose , Mutação
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA
...