RESUMEN
We examined DNA site recognition by Bicoid and its importance for pattern formation in developing Drosophila embryos. Using altered DNA specificity Bicoid mutants and appropriate reporter genes, we show that Bicoid distinguishes among related DNA-binding sites in vivo by a specific contact between amino acid 9 of its recognition alpha-helix (lysine 50 of the homeodomain) and bp 7 of the site. This result is consistent with our earlier results using Saccharomyces cerevisiae but differs from that predicted by crystallographic analysis of another homeodomain-DNA interaction. Our results also demonstrate that Bicoid binds directly to those genes whose transcription it regulates and that the amino acid 9 contact is necessary for Bicoid to direct anterior pattern formation. In both Drosophila embryos and yeast cells, Bicoid requires multiple binding sites to activate transcription of target genes. We find that the distance between binding sites is critical for Bicoid activation but that, unexpectedly, this critical distance differs between Drosophila and S. cerevisiae. This result suggests that Bicoid activation in Drosophila might require an ancillary protein(s) not present in S. cerevisiae.
Asunto(s)
Elementos Transponibles de ADN , Proteínas de Unión al ADN/metabolismo , Drosophila melanogaster/metabolismo , Proteínas de Homeodominio , Hormonas de Insectos/metabolismo , Saccharomyces cerevisiae/metabolismo , Transactivadores , Animales , Secuencia de Bases , Sitios de Unión , Proteínas de Drosophila , Drosophila melanogaster/embriología , Drosophila melanogaster/genética , Embrión no Mamífero/metabolismo , Femenino , Genes Homeobox , Hormonas de Insectos/biosíntesis , Hormonas de Insectos/genética , Masculino , Modelos Estructurales , Datos de Secuencia Molecular , Morfogénesis , Oligodesoxirribonucleótidos/síntesis química , Oligodesoxirribonucleótidos/metabolismo , Estructura Secundaria de Proteína , Saccharomyces cerevisiae/genéticaAsunto(s)
Evolución Molecular , Regulación de la Expresión Génica , Silenciador del Gen , Animales , Proteínas de Arabidopsis , Cromatina/genética , Cromatina/metabolismo , Metilación de ADN , Elementos Transponibles de ADN , Proteínas de Unión al ADN/genética , Proteínas de Unión al ADN/metabolismo , Plantas/genética , ARN Bicatenario/metabolismo , Secuencias Repetitivas de Ácidos Nucleicos , Factores de Transcripción/genética , Factores de Transcripción/metabolismo , Transcripción GenéticaRESUMEN
The structure of the endonuclease R.PvuII in the absence and presence of its recognition site indicates how the interaction with DNA might proceed.
Asunto(s)
Desoxirribonucleasas de Localización Especificada Tipo II/química , ADN/química , ADN/metabolismo , Desoxirribonucleasa EcoRI/química , Desoxirribonucleasas de Localización Especificada Tipo II/metabolismo , Conformación Proteica , Proteus vulgaris/enzimología , Relación Estructura-ActividadRESUMEN
Variation in ways in which proteins can identify and lock on to genes due for transcription is illuminated by studies of the Arc repressor, which has a beta-sheet, rather than alpha-helical, recognition motif.
Asunto(s)
Proteínas de Unión al ADN/metabolismo , ADN/metabolismo , Estructura Secundaria de Proteína , Proteínas Represoras/metabolismo , Proteínas Virales/metabolismo , Proteínas Bacterianas/química , Proteínas Bacterianas/metabolismo , Proteínas de Unión al ADN/química , Proteínas de Unión al ADN/genética , Mutagénesis , Regiones Operadoras Genéticas , Proteínas Represoras/química , Proteínas Represoras/genética , Proteína de Unión a TATA-Box , Factores de Transcripción/química , Factores de Transcripción/metabolismo , Proteínas Virales/química , Proteínas Virales/genética , Proteínas Reguladoras y Accesorias ViralesRESUMEN
Recent structures of members of the serine proteinase inhibitor families (serpins) continue to emphasize the flexibility of the reactive loop and suggest possible 'active' conformations.
Asunto(s)
Serpinas/química , Sitios de Unión , Humanos , Conformación Proteica , Serpinas/metabolismoRESUMEN
A double insight into visual accommodation by the eye lens in birds and into the activity of a superfamily of metabolic enzymes is provided by the structure of turkey lens delta-crystallin.
Asunto(s)
Cristalinas/química , Cristalino/fisiología , Acomodación Ocular , Animales , Evolución Biológica , Conformación Proteica , PavosRESUMEN
The x-ray crystal structure of endothelin reveals a peptide with a compact globular conformation that may well represent the active form of the molecule.
Asunto(s)
Endotelinas/química , Animales , Cristalografía por Rayos X , Endotelinas/metabolismo , Humanos , Ratones , Ratones Noqueados , Conformación Proteica , Receptores de Endotelina/metabolismoRESUMEN
Striped expression of the pair-rule gene hairy (h) plays a central role in regulating segmentation in Drosophila. We have used h-lacZ reporter gene fusions to delineate h sequences that drive individual stripe expression. We show that 14 kb of 5'-flanking DNA directs expression of seven lacZ stripes in the blastoderm embryo. Within this region, we identify discrete sequences required for expression of individual stripes 1, 5, 6, and 7, and dispersed elements active in the stripe 2 domain. Only the stripe 1 element directs lacZ expression in an accurate h stripe; stripes 5, 6, and 7 are displaced by one to two cells relative to their h counterparts. These results indicate that regulatory sequences are dispersed within the h promoter. We have determined the sensitivity of the lacZ stripes to maternal, gap, and pair-rule gene mutations. Our results suggest that different but overlapping subsets of gap genes regulate each stripe and that activation and repression are both important in generating the stripe pattern.
Asunto(s)
Proteínas de Drosophila , Drosophila/genética , Hormonas de Insectos/genética , Proteínas de Insectos , Regiones Promotoras Genéticas , Proteínas Represoras , Factores de Transcripción/genética , Animales , Secuencia de Bases , Factores de Transcripción con Motivo Hélice-Asa-Hélice Básico , Clonación Molecular , ADN , Datos de Secuencia Molecular , Fenotipo , Secuencias Reguladoras de Ácidos Nucleicos , Mapeo Restrictivo , beta-Galactosidasa/genéticaRESUMEN
It has previously been shown that a region of 100 bp in the Drosophila hsp27 promoter is sufficient to confer ecdysone inducibility on a heterologous gene. We now show, using binding and DNase I footprinting assays, that a 23-bp hyphenated dyad within this sequence forms a protein-binding site, and that this is sufficient for inducibility. The sequence shows partial homology with mammalian steroid receptor binding sites. UV crosslinking identifies an 80- to 90-kd protein that binds specifically to this sequence and is thus a candidate for the ecdysone receptor.
RESUMEN
Transcription of the Drosophila hsp27 gene is induced both by heat shock and by the steroid hormone ecdysone. Deletion analysis of the promoter using a transient expression assay in Drosophila tissue culture cells reveals two separate and functionally independent regulatory regions, whose positions coincide with previously reported DNase I-hypersensitive sites in embryonic chromatin. Ecdysone induction is mediated by multiple elements between -579 and -455. Several matches to the consensus heat shock regulatory element (HSE) lie between -370 and -270, and deletion of these abolishes the response to heat shock. Heat inducibility can be restored by the addition of HSE sequences from the hsp70 promoter, even when these are placed at the 3' end of the gene. Furthermore, HSEs seperated by >2 kb can interact in a cooperative way to promote transcription. Deletion of sequences adjacent to the TATA box (-40 to -154) has little effect on induction by either heat shock or ecdysone. In this respect, activation of the hsp27 TATA box in Drosophila cells differs from the long-range activation of promoters by HSEs or viral enhancers in HeLa cells.