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.
Mol Cell Biol ; 32(11): 2110-20, 2012 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-22451490

RESUMO

E2F and RB proteins regulate the expression of genes involved in cell cycle progression, apoptosis, differentiation, and development. Recent studies indicate that they function as part of an evolutionarily conserved multiprotein complex termed dREAM/DREAM/LINC. Here we characterize the role of the Drosophila complex, dREAM, in the regulation of differentiation-specific E2F target genes in actively proliferating cells. These genes are regulated differently from cell cycle-related E2F targets, they do not depend on E2F activation, and E2F/RB repression is maintained throughout the cell cycle. In proliferating cells, their repression is dependent on dREAM. We find that dREAM plays a dual role in their regulation. First, it is required for the stability of the repressive dE2F2/RBF complexes at their promoters during S phase. Second, we find that dREAM is indispensable for both transcriptional repression mechanisms employed at these genes.


Assuntos
Proteínas de Drosophila/genética , Drosophila melanogaster/genética , Fatores de Transcrição E2F/genética , Proteína do Retinoblastoma/genética , Animais , Ciclo Celular , Diferenciação Celular/genética , Regulação da Expressão Gênica , Complexos Multiproteicos/genética , Complexos Multiproteicos/metabolismo
2.
Biochim Biophys Acta ; 1819(1): 16-27, 2012 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-21978826

RESUMO

The histone genes are an important group of cell cycle regulated genes whose transcription is activated during the G1/S transition and repressed in early G1, late S, and G2/M. The HIR complex, comprised of Hir1, Hir2, Hir3 and Hpc2, regulates three of the four histone gene loci. While relief of repression at the G1/S boundary involves the HIR complex, as well as other cofactors, the mechanism by which this derepression occurs remains unknown. To better understand how transcriptional repression contributes to periodic expression in the cell cycle, we sought to identify the cell cycle signals required to alleviate HIR-mediated repression of the histone genes. By measuring histone gene transcription in strains with various combinations of clb mutations, we found that the mitotic Clb1/Clb2 cyclins are required to alleviate Hir-mediated repression during the G1/S transition and that Clb2 physically interacts with the HIR complex. While the HIR complex regulates histone gene transcription in combination with two other histone H3/H4 chaperones, Asf1 and Rtt106, our data demonstrate that the mitotic Clb cyclins are necessary to specifically alleviate the repressive action of the HIR complex itself in order to allow proper expression of the histone genes in late G1/early S phase.


Assuntos
Ciclina B/genética , Histonas/genética , Histonas/metabolismo , Proteínas Nucleares/genética , Proteínas Repressoras/genética , Proteínas de Saccharomyces cerevisiae/genética , Saccharomyces cerevisiae/genética , Proteínas de Ciclo Celular/genética , Proteínas de Ciclo Celular/metabolismo , Ciclina B/metabolismo , Ciclinas/genética , Ciclinas/metabolismo , Proteínas de Ligação a DNA/genética , Proteínas de Ligação a DNA/metabolismo , Proteínas F-Box/genética , Proteínas F-Box/metabolismo , Pontos de Checagem da Fase G1 do Ciclo Celular , Regulação Fúngica da Expressão Gênica , Mitose/genética , Chaperonas Moleculares/genética , Chaperonas Moleculares/metabolismo , Complexos Multiproteicos/genética , Mutação , Proteínas Nucleares/metabolismo , Regiões Promotoras Genéticas , Proteínas Repressoras/metabolismo , Saccharomyces cerevisiae/metabolismo , Proteínas de Saccharomyces cerevisiae/metabolismo , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo , Transcrição Gênica , Ubiquitina-Proteína Ligases/genética , Ubiquitina-Proteína Ligases/metabolismo
3.
Fly (Austin) ; 5(2): 115-8, 2011.
Artigo em Inglês | MEDLINE | ID: mdl-21150287

RESUMO

Inactivation of the retinoblastoma protein (pRB) is a hallmark of human cancer. Accordingly the RB pathway has been extensively studied in mammals, flies and worms, but mostly in the context of cell cycle entry. The means by which RB proteins regulate differentiation and the transcription of genes involved in differentiation and development is less well understood. We have examined how Drosophila RB proteins regulate differentiation-specific genes in proliferating cells. We found that the mechanism of repression differs from what has been observed at cell cycle regulated genes (Figure 1). Two different chromatin modifications present at different locations contribute to the repression of such genes. We argue that this represents a novel mechanism of repression and that this type of regulation by RB proteins warrants further attention.


Assuntos
Proteínas Adaptadoras de Transporte Vesicular/fisiologia , Proteínas de Drosophila/fisiologia , Drosophila/genética , Regulação da Expressão Gênica no Desenvolvimento , Acetilação , Proteínas Adaptadoras de Transporte Vesicular/genética , Proteínas Adaptadoras de Transporte Vesicular/metabolismo , Animais , Diferenciação Celular/genética , Proliferação de Células , Células Cultivadas , Montagem e Desmontagem da Cromatina , Drosophila/crescimento & desenvolvimento , Proteínas de Drosophila/genética , Proteínas de Drosophila/metabolismo , Epigênese Genética , Histonas/metabolismo , Metilação
4.
Mol Cell Biol ; 30(10): 2563-77, 2010 May.
Artigo em Inglês | MEDLINE | ID: mdl-20176807

RESUMO

The RB and E2F proteins play important roles in the regulation of cell division, cell death, and development by controlling the expression of genes involved in these processes. The mechanisms of repression by the retinoblastoma protein (pRB) have been extensively studied at cell cycle-regulated promoters. However, little is known about developmentally regulated E2F/RB genes. Here, we have taken advantage of the simplicity of the E2F/RB pathway in flies to inspect the regulation of differentiation-specific target genes. These genes are repressed by dE2F2/RBF and a recently identified RB-containing complex, dREAM/MMB, in a cell type- and cell cycle-independent manner. Our studies indicate that the mechanism of repression differs from that of cell cycle-regulated genes. We find that two different activities are involved in their regulation and that in proliferating cells, both are required to maintain repression. First, dE2F2/RBF and dREAM/MMB employ histone deacetylase (HDAC) activities at promoter regions. Remarkably, we have also uncovered an unconventional mechanism of repression by the Polycomb group (PcG) protein Enhancer of zeste [E(Z)], which is involved in silencing of these genes through the dimethylation of histone H3 Lys27 at nucleosomes located downstream of the transcription start sites (TSS).


Assuntos
Proteínas Adaptadoras de Transporte Vesicular/metabolismo , Diferenciação Celular/genética , Proteínas de Drosophila/metabolismo , Drosophila melanogaster/fisiologia , Fatores de Transcrição E2F/metabolismo , Regulação da Expressão Gênica , Proteínas Adaptadoras de Transporte Vesicular/genética , Animais , Células Cultivadas , Proteínas de Drosophila/genética , Fatores de Transcrição E2F/genética , Histona Desacetilases/metabolismo , Histonas/metabolismo , Humanos , Regiões Promotoras Genéticas
5.
Dev Cell ; 9(4): 463-75, 2005 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-16198289

RESUMO

E2F transcription factors are generally believed to be positive regulators of apoptosis. In this study, we show that dE2F1 and dDP are important for the normal pattern of DNA damage-induced apoptosis in Drosophila wing discs. Unexpectedly, the role that E2F plays varies depending on the position of the cells within the disc. In irradiated wild-type discs, intervein cells show a high level of DNA damage-induced apoptosis, while cells within the D/V boundary are protected. In irradiated discs lacking E2F regulation, intervein cells are largely protected, but apoptotic cells are found at the D/V boundary. The protective effect of E2F at the D/V boundary is due to a spatially restricted role in the repression of hid. These loss-of-function experiments demonstrate that E2F cannot be classified simply as a pro- or antiapoptotic factor. Instead, the overall role of E2F in the damage response varies greatly and depends on the cellular context.


Assuntos
Apoptose/fisiologia , Proteínas de Drosophila/metabolismo , Drosophila melanogaster/embriologia , Estruturas Embrionárias , Animais , Dano ao DNA , Proteínas de Drosophila/genética , Drosophila melanogaster/anatomia & histologia , Drosophila melanogaster/metabolismo , Estruturas Embrionárias/anatomia & histologia , Estruturas Embrionárias/fisiologia , Regulação da Expressão Gênica no Desenvolvimento , Genes Reporter , Hibridização In Situ , Mutação , Neuropeptídeos/genética , Neuropeptídeos/metabolismo , Interferência de RNA
6.
Cell Cycle ; 4(9): 1272-80, 2005 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-16082225

RESUMO

In higher eukaryotes, the Retinoblastoma and E2F families of proteins control the transcription of a large number of target genes. Here, we have mutated the second Drosophila Retinoblastoma family gene (Rbf2), and contrasted the in vivo molecular functions of RBF2 with dE2F2, the only E2F partner of RBF2. Previous studies failed to uncover a unique role for RBF2 in E2F regulation. Here we find that RBF2 functions in concert with dE2F2 in vivo to repress the expression of differentiation markers in ovaries and embryos where RBF2 is highly expressed. We have compared the profiles of transcripts that are mis-expressed in ovaries, embryos and S2 cells where RBF2 function has been ablated and find that RBF2 and dE2F2 control strikingly different transcriptional programs in each situation. In vivo promoter occupancy studies point to the redistribution of dE2F/RBF complexes to different promoters in different cell types as one mechanism governing the tissue-specific regulation of dE2F/RBF target genes. These results demonstrate that RBF2 has a unique function in repressing E2F-regulated differentiation markers and that dE2F2 and RBF2 are required to regulate different sets of target genes in different tissues.


Assuntos
Proteínas de Drosophila/metabolismo , Proteínas de Drosophila/fisiologia , Drosophila melanogaster/fisiologia , Fator de Transcrição E2F2/metabolismo , Proteínas Repressoras/fisiologia , Alelos , Animais , Northern Blotting , Cromatina/química , Imunoprecipitação da Cromatina , Cruzamentos Genéticos , Drosophila melanogaster/genética , Embrião não Mamífero/metabolismo , Feminino , Deleção de Genes , Regulação da Expressão Gênica , Genoma , Homozigoto , Masculino , Microscopia Eletrônica de Varredura , Modelos Biológicos , Modelos Genéticos , Mutação , Análise de Sequência com Séries de Oligonucleotídeos , Ovário/metabolismo , Fenótipo , Regiões Promotoras Genéticas , Estrutura Terciária de Proteína , Proteínas Repressoras/metabolismo , Transgenes
7.
Genes Dev ; 17(18): 2308-20, 2003 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-12975318

RESUMO

To determine which E2F/RB-family members are functionally important at E2F-dependent promoters, we used RNA interference (RNAi) to selectively remove each component of the dE2F/dDP/RBF pathway, and we examined the genome-wide changes in gene expression that occur when each element is missing. The results reveal a remarkable division of labor between family members. Classic E2F targets, encoding functions needed for cell cycle progression, are expressed in cycling cells and are primarily dependent on dE2F1and RBF1 for regulation. Unexpectedly, there is a second program of dE2F/RBF-dependent transcription, in which dE2F2/RBF1or dE2F2/RBF2 complexes repress gene expression in actively proliferating cells. These new E2F target genes encode differentiation factors that are transcribed in developmentally regulated and gender-specific patterns and not in a cell cycle-regulated manner. We propose that dE2F/RBF complexes should not be viewed simply as a cell cycle regulator of transcription. Instead, dE2F/RBF-mediated repression is exerted on genes that encode an assortment of cellular functions, and these effects are reversed on sets of functionally related genes in particular developmental contexts. As a result, dE2F/RBF regulation is used to link gene expression with cell cycle progression at some targets while simultaneously providing stable repression at others.


Assuntos
Proteínas Adaptadoras de Transporte Vesicular/metabolismo , Ciclo Celular/fisiologia , Proteínas de Drosophila/metabolismo , Drosophila/embriologia , Regulação da Expressão Gênica no Desenvolvimento/fisiologia , Fatores de Transcrição/metabolismo , Animais , Drosophila/genética , Fatores de Transcrição E2F , Análise de Sequência com Séries de Oligonucleotídeos , Regiões Promotoras Genéticas , Transcrição Gênica/fisiologia
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA
...