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2.
EMBO J ; 19(18): 4997-5006, 2000 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-10990463

RESUMO

Arabidopsis HY5 is a bZIP transcription factor that promotes photomorphogenesis. Previous studies suggested that COP1, a negative regulator of photomorphogenesis, directly interacts with nuclear HY5 and targets it for proteasome-mediated degradation. Light negatively regulates the nuclear level of COP1 and thus permits HY5 accumulation. Here we report that HY5 abundance peaks in early seedling development, consistent with its role in promoting photomorphogenesis. HY5 acts exclusively within a complex and exists in two isoforms, resulting from phosphorylation within its COP1 binding domain by a light- regulated kinase activity. Unphosphorylated HY5 shows stronger interaction with COP1, is the preferred substrate for degradation, has higher affinity to target promoters and is physiologically more active than the phosphorylated version. Therefore, HY5 phosphorylation provides an added level of light-mediated regulation of HY5 stability and activity besides nuclear COP1 levels. Regulated HY5 phosphorylation not only provides abundant and physiologically more active unphosphorylated HY5 in the light, but also helps to maintain a small pool of less active phosphorylated HY5 in the dark, which could be essential for a rapid initial response during dark-to-light transition.


Assuntos
Proteínas de Arabidopsis , Arabidopsis/química , Proteínas de Transporte/metabolismo , Proteínas Nucleares/química , Proteínas Nucleares/genética , Proteínas Nucleares/metabolismo , Proteínas de Plantas/metabolismo , Ubiquitina-Proteína Ligases , Sequência de Aminoácidos , Fatores de Transcrição de Zíper de Leucina Básica , Sítios de Ligação , Western Blotting , Proteínas de Transporte/química , Caseína Quinase II , Núcleo Celular/metabolismo , Cromatografia em Gel , Glutationa Transferase/metabolismo , Luz , Dados de Sequência Molecular , Fosforilação , Proteínas de Plantas/química , Plantas Geneticamente Modificadas , Testes de Precipitina , Regiões Promotoras Genéticas , Isoformas de Proteínas , Proteínas Serina-Treonina Quinases/metabolismo , Estrutura Terciária de Proteína , Proteínas Recombinantes de Fusão/química , Proteínas Recombinantes de Fusão/metabolismo , Homologia de Sequência de Aminoácidos , Fatores de Tempo , Distribuição Tecidual , Fatores de Transcrição/química , Fatores de Transcrição/metabolismo , Transgenes , Técnicas do Sistema de Duplo-Híbrido
3.
Nature ; 405(6785): 462-6, 2000 May 25.
Artigo em Inglês | MEDLINE | ID: mdl-10839542

RESUMO

Arabidopsis seedlings display contrasting developmental patterns depending on the ambient light. Seedlings grown in the light develop photomorphogenically, characterized by short hypocotyls and expanded green cotyledons. In contrast, seedlings grown in darkness become etiolated, with elongated hypocotyls and dosed cotyledons on an apical hook. Light signals, perceived by multiple photoreceptors and transduced to downstream regulators, dictate the extent of photomorphogenic development in a quantitative manner. Two key downstream components, COP1 and HY5, act antagonistically in regulating seedling development. HY5 is a bZIP transcription factor that binds directly to the promoters of light-inducible genes, promoting their expression and photomorphogenic development. COP1 is a RING-finger protein with WD-40 repeats whose nuclear abundance is negatively regulated by light. COP1 interacts directly with HY5 in the nucleus to regulate its activity negatively. Here we show that the abundance of HY5 is directly correlated with the extent of photomorphogenic development, and that the COP1-HY5 interaction may specifically target HY5 for proteasome-mediated degradation in the nucleus.


Assuntos
Proteínas de Arabidopsis , Arabidopsis/crescimento & desenvolvimento , Proteínas Nucleares/fisiologia , Proteínas de Plantas/fisiologia , Ubiquitina-Proteína Ligases , Arabidopsis/efeitos da radiação , Fatores de Transcrição de Zíper de Leucina Básica , Proteínas de Transporte/fisiologia , Cisteína Endopeptidases/metabolismo , Escuridão , Luz , Dados de Sequência Molecular , Complexos Multienzimáticos/metabolismo , Proteínas Nucleares/genética , Proteínas Nucleares/metabolismo , Complexo de Proteínas do Centro de Reação Fotossintética/metabolismo , Proteínas de Plantas/genética , Plantas Geneticamente Modificadas , Complexo de Endopeptidases do Proteassoma , RNA Mensageiro/metabolismo
4.
Trends Cell Biol ; 9(3): 113-8, 1999 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-10201077

RESUMO

Photomorphogenic development in Arabidopsis is regulated by the key repressor COP1, which interacts with specific transcription factors in the nucleus to modulate their activities. In the dark, COP1 accumulates in the nucleus and represses photomorphogenic development. Light diminishes the nuclear accumulation of COP1 and abrogates its repressor activity. A number of cellular components are involved in light-dependent nucleocytoplasmic partitioning of COP1, including the multisubunit COP9 complexes and at least three well-characterized photoreceptors. This review discusses current understanding of the mechanisms of COP1 action.


Assuntos
Proteínas de Arabidopsis , Proteínas de Transporte/fisiologia , Proteínas de Ligação ao GTP , Proteínas de Plantas/fisiologia , Proteínas Repressoras , Ubiquitina-Proteína Ligases , Arabidopsis/fisiologia , Sítios de Ligação , Complexo do Signalossomo COP9 , Proteínas de Transporte/metabolismo , Núcleo Celular/metabolismo , Peptídeos e Proteínas de Sinalização Intracelular , Luz , Proteínas Nucleares/metabolismo , Complexo de Proteínas do Centro de Reação Fotossintética , Proteínas de Plantas/metabolismo , Proteínas/metabolismo , Fatores de Transcrição/metabolismo
5.
Plant J ; 16(2): 201-8, 1998 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-9839465

RESUMO

The subcellular localization of COP1, a key photomorphogenic repressor, is regulated by light in Arabidopsis seedlings. Photoreceptor loss-of-function mutants and dominant gain-of-function overexpression transgenes were both used to analyze the influences of the three photoreceptors, phyA, phyB, and CRY1, on the light-regulated subcellular localization of COP1. Through a semiquantitative analysis of the nuclear abundance of GUS-COP1 in the various genetic backgrounds, the specific roles of the individual photoreceptors have been established. The data suggest that multiple photoreceptors influence the light-regulated subcellular localization of COP1 in white light. Under specific wavelengths of light, phyA, phyB, and CRY1 each play critical roles in mediating far-red, red, and blue light signals, respectively. Our data also support an interdependency between CRY1 and the phytochromes in mediating the light-regulated subcellular localization of COP1 and thus seedling development.


Assuntos
Proteínas de Arabidopsis , Arabidopsis/metabolismo , Proteínas de Transporte/metabolismo , Núcleo Celular/metabolismo , Proteínas de Drosophila , Proteínas do Olho , Células Fotorreceptoras de Invertebrados , Células Fotorreceptoras , Complexo de Proteínas do Centro de Reação Fotossintética/metabolismo , Proteínas de Plantas/metabolismo , Proteínas Repressoras/metabolismo , Fatores de Transcrição , Ubiquitina-Proteína Ligases , Arabidopsis/efeitos da radiação , Proteínas de Transporte/genética , Proteínas de Transporte/efeitos da radiação , Núcleo Celular/efeitos da radiação , Criptocromos , Flavoproteínas/metabolismo , Genes Reporter , Glucuronidase/genética , Glucuronidase/metabolismo , Luz , Complexo de Proteínas do Centro de Reação Fotossintética/efeitos da radiação , Fitocromo/metabolismo , Fitocromo A , Fitocromo B , Proteínas de Plantas/genética , Proteínas de Plantas/efeitos da radiação , Receptores Acoplados a Proteínas G , Proteínas Recombinantes de Fusão/genética , Proteínas Recombinantes de Fusão/metabolismo , Proteínas Repressoras/genética , Proteínas Repressoras/efeitos da radiação , Sementes/genética , Sementes/metabolismo , Sementes/efeitos da radiação , Transgenes
6.
Plant Physiol ; 114(3): 779-88, 1997 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-9232869

RESUMO

Using a beta-glucuronidase (GUS) reporter-COP1 fusion transgene, it was shown previously that Arabidopsis COP1 acts within the nucleus as a repressor of seedling photomorphogenic development and that high inactivation of COP1 was accompanied by a reduction of COP1 nuclear abundance (A.G. von Arnim, X.-W. Deng [1994] Cell 79: 1035-1045). Here we report that the GUS-COP1 fusion transgene can completely rescue the defect of cop1 mutations and thus is fully functional during seedling development. The kinetics of GUS-COP1 relocalization in a cop1 null mutant background during dark/light transitions imply that the regulation of the functional nuclear COP1 level plays a role in stably maintaining a committed seedling's developmental fate rather than in causing such a commitment. Analysis of GUS-COP1 cellular localization in mutant hypocotyls of all pleiotropic COP/DET/FUS loci revealed that nuclear localization of GUS-COP1 was diminished under both dark and light conditions in all mutants tested, whereas nuclear localization was not affected in the less pleiotropic cop4 mutant. Using both the brassinosteroid-deficient mutant det2 and brassinosteroid treatment of wild-type seedlings, we have demonstrated that brassinosteroid does not control the hypocotyl cell elongation through regulation nuclear localization of COP1. The growth regulator cytokinin, which also dramatically reduced hypocotyl cell elongation in the absence of light, did not prevent GUS-COP1 nuclear localization in dark-grown seedlings. Our results suggest that all of the previously characterized pleiotropic COP/DET/FUS loci are required for the proper nuclear localization of the COP1 protein in the dark, whereas the less pleiotropic COP/DET loci or plant regulators tested are likely to act either downstream of COP1 or by independent pathways.


Assuntos
Proteínas de Arabidopsis , Arabidopsis/fisiologia , Proteínas de Transporte/biossíntese , Núcleo Celular/metabolismo , Regulação da Expressão Gênica no Desenvolvimento , Proteínas de Plantas/biossíntese , Proteínas Repressoras/biossíntese , Ubiquitina-Proteína Ligases , Arabidopsis/genética , Proteínas de Transporte/genética , Cruzamentos Genéticos , Escuridão , Glucuronidase/biossíntese , Hipocótilo , Luz , Morfogênese/fisiologia , Morfogênese/efeitos da radiação , Mutagênese , Fenótipo , Reguladores de Crescimento de Plantas/fisiologia , Proteínas de Plantas/genética , Plantas Geneticamente Modificadas , Proteínas Recombinantes de Fusão , Recombinação Genética , Proteínas Repressoras/genética
7.
Cell ; 86(1): 115-21, 1996 Jul 12.
Artigo em Inglês | MEDLINE | ID: mdl-8689678

RESUMO

Arabidopsis COP9 is a component of a large protein complex that is essential for the light control of a developmental switch and whose conformation or size is modulated by light. The complex is acidic, binds heparin, and is localized within the nucleus. Biochemical purification of the complex to near homogeneity revealed that it contains 12 distinct subunits. One of the other subunits is COP11, mutations in which result in a phenotype identical to cop9 mutants. The COP9 complex may act to regulate the nuclear abundance of COP1, an established repressor of photomorphogenic development. During the biogenesis of the COP9 complex, a certain degree of prior subunit association is a prerequisite for proper nuclear translocation. Since both COP9 and COP11 have closely related human counterparts, the COP9 complex probably represents a conserved developmental regulator in higher eukaryotes.


Assuntos
Proteínas de Arabidopsis , Arabidopsis/embriologia , Proteínas de Plantas/genética , Proteínas , Ubiquitina-Proteína Ligases , Complexo do Signalossomo COP9 , Proteínas de Transporte/metabolismo , Núcleo Celular/química , Núcleo Celular/metabolismo , Escuridão , Regulação da Expressão Gênica no Desenvolvimento/fisiologia , Regulação da Expressão Gênica de Plantas/fisiologia , Genes de Plantas/fisiologia , Complexos Multiproteicos , Peptídeo Hidrolases , Proteínas de Plantas/isolamento & purificação , Proteínas de Plantas/metabolismo , Proteínas de Plantas/ultraestrutura , Proteínas Repressoras/metabolismo
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