RESUMEN

Merkel cell carcinoma is an uncommon primary neuroendocrine neoplasm of the skin that may exhibit divergent differentiation. However, rhabdomyosarcomatous differentiation has only been rarely described and takes the form of isolated rhabdomyoblasts. We describe a case of cutaneous Merkel cell carcinoma with biphasic morphology imparted by discrete patches of embryonal rhabdomyosarcoma-like spindle cells alternating with islands of neuroendocrine small round cells, justifying a designation of "Merkel cell carcinosarcoma." The former component showed positive immunostaining for desmin and myogenin; and the later component, pan-cytokeratin, cytokeratin 20, synaptophysin, and chromogranin. The patient was an elderly man who presented with a temporal skin mass, and the biphasic morphology was evident in the recurrence and metastasis that developed 2 months after incomplete excision of the skin lesion.

Asunto(s)

Carcinoma de Células de Merkel/patología , Rabdomiosarcoma Embrionario/patología , Neoplasias Cutáneas/patología , Anciano de 80 o más Años , Biomarcadores de Tumor/metabolismo , Carcinoma de Células de Merkel/metabolismo , Carcinoma de Células de Merkel/cirugía , Resultado Fatal , Humanos , Masculino , Recurrencia Local de Neoplasia , Neoplasias Primarias Múltiples , Rabdomiosarcoma Embrionario/metabolismo , Rabdomiosarcoma Embrionario/cirugía , Neoplasias Cutáneas/metabolismo , Neoplasias Cutáneas/cirugía

RESUMEN

Extensive studies in vertebrate cells have assigned a central role to Rel/NF-kappa B and AP-1 family members in the control of apoptosis. We ask here whether parallel pathways might function in Drosophila by determining if Rel/NF-kappa B or AP-1 family members contribute to the steroid-triggered death of larval salivary glands during Drosophila metamorphosis. We show that two of the three Drosophila Rel/NF-kappa B genes are expressed in doomed salivary glands and that one family member, Dif, is induced in a stage-specific manner immediately before the onset of programmed cell death. Similarly, Djun is expressed for many hours before salivary gland cell death while Dfos is induced in a stage-specific manner, immediately before this tissue is destroyed. We show that null mutations in the three Drosophila Rel/NF-kappa B family members, either alone or in combination, have no apparent effect on this death response. In contrast, Dfos is required for the proper timing of larval salivary gland cell death as well as the proper induction of key death genes. This study demonstrates a role for AP-1 in the stage-specific steroid-triggered programmed cell death of larval tissues during Drosophila metamorphosis.

Asunto(s)

Apoptosis/fisiología , Proteínas de Drosophila , FN-kappa B/metabolismo , Glándulas Salivales/fisiología , Factor de Transcripción AP-1/metabolismo , Animales , Proteínas de Unión al ADN/genética , Proteínas de Unión al ADN/metabolismo , Drosophila , Proteínas de Insectos/genética , Proteínas de Insectos/metabolismo , Larva/citología , Larva/efectos de los fármacos , Metamorfosis Biológica/fisiología , Mutación , FN-kappa B/genética , FN-kappa B/fisiología , Neuropéptidos/biosíntesis , Neuropéptidos/metabolismo , Péptidos/metabolismo , Glándulas Salivales/citología , Glándulas Salivales/efectos de los fármacos , Esteroides/farmacología , Factor de Transcripción AP-1/genética , Factor de Transcripción AP-1/fisiología , Factores de Transcripción/biosíntesis , Factores de Transcripción/metabolismo

RESUMEN

Delaminated neuroblasts in Drosophila function as stem cells during embryonic central nervous system development. They go through repeated asymmetric divisions to generate multiple ganglion mother cells, which divide only once more to produce postmitotic neurons. Snail, a zinc-finger transcriptional repressor, is a pan-neural protein, based on its extensive expression in neuroblasts. Previous results have demonstrated that Snail and related proteins, Worniu and Escargot, have redundant and essential functions in the nervous system. We show that the Snail family of proteins control central nervous system development by regulating genes involved in asymmetry and cell division of neuroblasts. In mutant embryos that have the three genes deleted, the expression of inscuteable is significantly lowered, while the expression of other genes that participate in asymmetric division, including miranda, staufen and prospero, appears normal. The deletion mutants also have much reduced expression of string, suggesting that a key component that drives neuroblast cell division is abnormal. Consistent with the gene expression defects, the mutant embryos lose the asymmetric localization of prospero RNA in neuroblasts and lose the staining of Prospero protein that is normally present in ganglion mother cells. Simultaneous expression of inscuteable and string in the snail family deletion mutant efficiently restores Prospero expression in ganglion mother cells, demonstrating that the two genes are key targets of Snail in neuroblasts. Mutation of the dCtBP co-repressor interaction motifs in the Snail protein leads to reduction of the Snail function in central nervous system. These results suggest that the Snail family of proteins control both asymmetry and cell division of neuroblasts by activating, probably indirectly, the expression of inscuteable and string.

Asunto(s)

Proteínas del Citoesqueleto/genética , Proteínas de Unión al ADN/metabolismo , Proteínas de Drosophila , Drosophila/embriología , Drosophila/genética , Genes de Insecto , Neuronas/metabolismo , Fosfoproteínas Fosfatasas/genética , Proteínas Tirosina Fosfatasas , Factores de Transcripción/metabolismo , Animales , Tipificación del Cuerpo/genética , Ciclo Celular/genética , Proteínas de Ciclo Celular , División Celular/genética , Sistema Nervioso Central/citología , Sistema Nervioso Central/embriología , Sistema Nervioso Central/metabolismo , Drosophila/citología , Drosophila/metabolismo , Eliminación de Gen , Regulación del Desarrollo de la Expresión Génica , Hibridación in Situ , Proteínas del Tejido Nervioso/genética , Neuronas/citología , Neuropéptidos , Proteínas Nucleares/genética , ARN Mensajero/genética , ARN Mensajero/metabolismo , Factores de Transcripción de la Familia Snail , Células Madre/citología , Células Madre/metabolismo , Factores de Transcripción/genética

RESUMEN

Multiple endocrine neoplasia type 1 (MEN1) is a familial cancer syndrome characterized by tumors of the parathyroid, entero-pancreatic neuroendocrine and pituitary tissues and caused by inactivating mutations in the MEN1 gene. Menin, the 610-amino acid nuclear protein encoded by MEN1, binds to the transcription factor JunD and can repress JunD-induced transcription. We report here the identification of a MEN1 ortholog in Drosophila melanogaster, Menin1, that encodes a 763 amino acid protein sharing 46% identity with human menin. Additionally, 69% of the missense mutations and in-frame deletions reported in MEN1 patients appear in amino acid residues that are identical in the Drosophila and human protein, suggesting the importance of the conserved regions. Drosophila Menin1 gene transcripts use alternative polyadenylation sites resulting in 4.3 and 5-kb messages. The 4.3-kb transcript appears to be largely maternal, while the 5-kb transcript appears mainly zygotic. The binding of Drosophila menin to human JunD or Drosophila Jun could not be demonstrated by the yeast two-hybrid analysis. The identification of the MEN1 ortholog from Drosophila melanogaster will provide an opportunity to utilize Drosophila genetics to enhance our understanding of the function of human menin.

Asunto(s)

Drosophila melanogaster/genética , Proteínas de Neoplasias/genética , Proteínas Proto-Oncogénicas , Secuencia de Aminoácidos , Animales , Northern Blotting , ADN Complementario/química , ADN Complementario/genética , Drosophila melanogaster/embriología , Drosophila melanogaster/crecimiento & desarrollo , Embrión no Mamífero/metabolismo , Desarrollo Embrionario , Exones , Femenino , Regulación del Desarrollo de la Expresión Génica , Genes de Insecto/genética , Glutatión Transferasa/genética , Glutatión Transferasa/metabolismo , Humanos , Hibridación in Situ , Intrones , Masculino , Ratones , Datos de Secuencia Molecular , Proteínas Proto-Oncogénicas c-jun/genética , Proteínas Proto-Oncogénicas c-jun/metabolismo , ARN Mensajero/genética , ARN Mensajero/metabolismo , Ratas , Proteínas Recombinantes de Fusión/genética , Proteínas Recombinantes de Fusión/metabolismo , Saccharomyces cerevisiae/genética , Alineación de Secuencia , Análisis de Secuencia de ADN , Homología de Secuencia , Transcripción Genética , Técnicas del Sistema de Dos Híbridos , Pez Cebra

RESUMEN

The existence of homologous genes in diverse species is intriguing. A detailed comparison of the structure and function of gene families may provide important insights into gene regulation and evolution. An unproven assumption is that homologous genes have a common ancestor. During evolution, the original function of the ancestral gene might be retained in the different species which evolved along separate courses. In addition, new functions could have developed as the sequence began to diverge. This may also explain partly the presence of multipurpose genes, which have multiple functions at different stages of development and in different tissues. The Drosophila gene snail is a multipurpose gene; it has been demonstrated that snail is critical for mesoderm formation, for CNS development, and for wing cell fate determination. The related vertebrate Snail and Slug genes have also been proposed to participate in mesoderm formation, neural crest cell migration, carcinogenesis, and apoptosis. In this review, we will discuss the Snail/Slug family of regulators in species ranging from insect to human. We will present the protein structures, expression patterns, and functions based on molecular genetic analyses. We will also include the studies that helped to elucidate the molecular mechanisms of repression and the relationship between the conserved and divergent functions of these genes. Moreover, the studies may enable us to trace the evolution of this gene family.

Asunto(s)

Proteínas de Unión al ADN/genética , Factores de Transcripción/genética , Animales , Proteínas de Unión al ADN/fisiología , Evolución Molecular , Regulación del Desarrollo de la Expresión Génica , Humanos , Neoplasias/genética , Factores de Transcripción de la Familia Snail , Factores de Transcripción/fisiología

RESUMEN

Snail/Slug family proteins have been identified in diverse species of both vertebrates and invertebrates. The proteins contain four to six zinc fingers and function as DNA-binding transcriptional regulators. Various members of the family have been demonstrated to regulate cell movement, neural cell fate, left-right asymmetry, cell cycle, and apoptosis. However, the molecular mechanisms of how these regulators function and the target genes involved are largely unknown. In this report, we demonstrate that human Slug (hSlug) is a repressor and modulates both activator-dependent and basal transcription. The repression depends on the C-terminal DNA-binding zinc fingers and on a separable repression domain located in the N terminus. This domain may recruit histone deacetylases to modify the chromatin and effect repression. Protein localization study demonstrates that hSlug is present in discrete foci in the nucleus. This subnuclear pattern does not colocalize with the PML foci or the coiled bodies. Instead, the hSlug foci overlap extensively with areas of the SC-35 staining, some of which have been suggested to be sites of active splicing or transcription. These results lead us to postulate that hSlug localizes to target promoters, where activation occurs, to repress basal and activator-mediated transcription.

Asunto(s)

Núcleo Celular/metabolismo , Proteínas Nucleares , Proteínas Represoras/metabolismo , Factores de Transcripción/genética , Factores de Transcripción/metabolismo , Transcripción Genética , Secuencia de Bases , Sitios de Unión , Núcleo Celular/genética , Cromatina/metabolismo , Secuencia Conservada , Proteínas de Unión al ADN/metabolismo , Inhibidores Enzimáticos/farmacología , Técnica del Anticuerpo Fluorescente , Inhibidores de Histona Desacetilasas , Histona Desacetilasas/metabolismo , Humanos , Ácidos Hidroxámicos/farmacología , Datos de Secuencia Molecular , Proteínas de Neoplasias/inmunología , Proteínas de Neoplasias/metabolismo , Proteína de la Leucemia Promielocítica , Empalme del ARN , Proteínas Represoras/genética , Proteínas Represoras/inmunología , Eliminación de Secuencia , Factores de Transcripción de la Familia Snail , Factores de Transcripción/inmunología , Proteínas Supresoras de Tumor , Dedos de Zinc

RESUMEN

The Snail protein functions as a transcriptional regulator to establish early mesodermal cell fate. Later, in germ band-extended embryos, Snail is also expressed in most neuroblasts. Here we present evidence that this expression of Snail is required for central nervous system (CNS) development. The neural function of snail is masked by two closely linked genes, escargot and worniu. Both Escargot and Worniu contain zinc-finger domains that are highly homologous to that of Snail. Although not affecting expression of early neuroblast markers, the deletion of the region containing all three genes correlates with loss of expression of CNS determinants including fushi tarazu, pdm-2 and even-skipped. Transgenic expression of each of the three Snail family proteins can rescue efficiently the fushi tarazu defects, and partially the pdm-2 and even-skipped CNS patterns. These results demonstrate that the Snail family proteins have essential functions during embryonic CNS development, around the time of ganglion mother cell formation.

Asunto(s)

Proteínas Bacterianas , Proteínas de Unión al ADN/genética , Proteínas de Drosophila , Drosophila melanogaster/embriología , Drosophila melanogaster/genética , Sistema Nervioso/embriología , Neuronas/fisiología , Factores de Transcripción/genética , Secuencia de Aminoácidos , Animales , Animales Modificados Genéticamente , Secuencia Conservada , Proteínas de Unión al ADN/biosíntesis , Proteínas de Unión al ADN/química , Embrión no Mamífero/fisiología , Factores de Transcripción Fushi Tarazu , Regulación del Desarrollo de la Expresión Génica , Proteínas de Homeodominio/genética , Datos de Secuencia Molecular , Alineación de Secuencia , Eliminación de Secuencia , Homología de Secuencia de Aminoácido , Factores de Transcripción de la Familia Snail , Factores de Transcripción/biosíntesis , Factores de Transcripción/química , Dedos de Zinc

RESUMEN

NF-kappaB/Rel family proteins regulate genes that are critical for many cellular processes including apoptosis, inflammation, immune response, and development. NF-kappaB/Rel proteins function as homodimers or heterodimers, which recognize specific DNA sequences within target promoters. We examined the activity of different Drosophila Rel-related proteins in modulating Drosophila immunity genes by expressing the Rel proteins in stably transfected cell lines. We also compared how different combinations of these transcriptional regulators control the activity of various immunity genes. The results show that Rel proteins are directly involved in regulating the Drosophila antimicrobial response. Furthermore, the drosomycin and defensin expression is best induced by the Relish/Dif and the Relish/Dorsal heterodimers, respectively, whereas the attacin activity can be efficiently up-regulated by the Relish homodimer and heterodimers. These results illustrate how the formation of Rel protein dimers differentially regulate target gene expression.

Asunto(s)

Drosophila/genética , Drosophila/inmunología , Regulación de la Expresión Génica/inmunología , Inmunidad/genética , FN-kappa B/genética , Proteínas Oncogénicas de Retroviridae/genética , Animales , Genes de Insecto/inmunología , FN-kappa B/inmunología , Proteínas Oncogénicas v-rel , Proteínas Oncogénicas de Retroviridae/inmunología

RESUMEN

The induction of immunity genes in Drosophila has been proposed to be dependent on Dorsal, Dif, and Relish, the NF-kappaB-related factors. Here we provide genetic evidence that Dif is required for the induction of only a subset of antimicrobial peptide genes. The results show that the presence of Dif without Dorsal is sufficient to mediate the induction of drosomycin and defensin. We also demonstrate that Dif is a downstream component of the Toll signaling pathway in activating the drosomycin expression. These results reveal that individual members of the NF-kappaB family in Drosophila have distinct roles in immunity and development.

Asunto(s)

Proteínas de Unión al ADN/genética , Proteínas de Drosophila , Drosophila/genética , Proteínas de Insectos/genética , Glicoproteínas de Membrana/genética , Receptores de Superficie Celular , Proteínas Ribosómicas , Proteína de Unión a Andrógenos/genética , Proteína de Unión a Andrógenos/metabolismo , Animales , Antibacterianos/metabolismo , Northern Blotting , Proteínas de Unión al ADN/metabolismo , Defensinas , Drosophila/inmunología , Exones , Genes de Insecto , Proteínas de Insectos/metabolismo , Intrones , Glicoproteínas de Membrana/metabolismo , Modelos Genéticos , FN-kappa B/genética , FN-kappa B/metabolismo , Proteínas/metabolismo , Transducción de Señal , Factores de Tiempo , Receptores Toll-Like , Factores de Transcripción/genética , Factores de Transcripción/metabolismo

RESUMEN

It is becoming increasingly clear that chromatin modification plays a fundamental part in transcriptional control. Recent studies provide new insights into how transcriptional repressors, in addition to blocking activators, may recruit repression complexes that include chromatin modification factors.

Asunto(s)

Cromatina/fisiología , Proteínas Cromosómicas no Histona , Proteínas de Unión al ADN/fisiología , Regulación de la Expresión Génica/fisiología , Histona Desacetilasas , Proteínas de Saccharomyces cerevisiae , Transcripción Genética/fisiología , Oxidorreductasas de Alcohol , Animales , Factores de Transcripción con Motivo Hélice-Asa-Hélice Básico , Ciclo Celular/fisiología , Cromatina/genética , Cromatina/metabolismo , Islas de CpG , Metilación de ADN , Drosophila melanogaster/genética , Drosophila melanogaster/fisiología , Humanos , Proteína 2 de Unión a Metil-CpG , Modelos Genéticos , Fosfoproteínas/fisiología , Proteínas/fisiología , Proteínas Represoras/fisiología , Factores de Transcripción/fisiología , Dedos de Zinc/fisiología

RESUMEN

Accumulating evidence suggests that the insect and mammalian innate immune response is mediated by homologous regulatory components. Proinflammatory cytokines and bacterial lipopolysaccharide stimulate mammalian immunity by activating transcription factors such as NF-kappaB and AP-1. One of the responses evoked by these stimuli is the initiation of a kinase cascade that leads to the phosphorylation of p38 mitogen-activated protein (MAP) kinase on Thr and Tyr within the motif Thr-Gly-Tyr, which is located within subdomain VIII. We have investigated the possible involvement of the p38 MAP kinase pathway in the Drosophila immune response. Two genes that are highly homologous to the mammalian p38 MAP kinase were molecularly cloned and characterized. Furthermore, genes that encode two novel Drosophila MAP kinase kinases, D-MKK3 and D-MKK4, were identified. D-MKK3 is an efficient activator of both Drosophila p38 MAP kinases, while D-MKK4 is an activator of D-JNK but not D-p38. These data establish that Drosophila indeed possesses a conserved p38 MAP kinase signaling pathway. We have examined the role of the D-p38 MAP kinases in the regulation of insect immunity. The results revealed that one of the functions of D-p38 is to attenuate antimicrobial peptide gene expression following exposure to lipopolysaccharide.

Asunto(s)

Proteínas Quinasas Dependientes de Calcio-Calmodulina/fisiología , Proteínas de Drosophila , Drosophila/genética , Drosophila/inmunología , Regulación de la Expresión Génica , Inmunidad/genética , Quinasas de Proteína Quinasa Activadas por Mitógenos , Proteínas Quinasas Activadas por Mitógenos , Secuencia de Aminoácidos , Animales , Animales Modificados Genéticamente , Antibacterianos/metabolismo , Antiinflamatorios/farmacología , Secuencia de Bases , Proteínas Quinasas Dependientes de Calcio-Calmodulina/genética , Proteínas Quinasas Dependientes de Calcio-Calmodulina/metabolismo , Clonación Molecular , Secuencia Conservada , Inhibidores Enzimáticos/farmacología , Imidazoles/farmacología , Proteínas de Insectos/biosíntesis , Proteínas de Insectos/genética , MAP Quinasa Quinasa 3 , Datos de Secuencia Molecular , Proteínas Serina-Treonina Quinasas/genética , Proteínas Serina-Treonina Quinasas/metabolismo , Proteínas Tirosina Quinasas/genética , Proteínas Tirosina Quinasas/metabolismo , Piridinas/farmacología , Proteínas Quinasas p38 Activadas por Mitógenos

RESUMEN

The c-Jun amino-terminal kinase (JNK) group of MAP kinases has been identified in mammals and insects. JNK is activated by exposure of cells to cytokines or environmental stress, indicating that this signaling pathway may contribute to inflammatory responses. Genetic and biochemical studies demonstrate that this signaling pathway also regulates cellular proliferation, apoptosis, and tissue morphogenesis. A functional role for JNK is therefore established in both the cellular response to stress and in many normal physiological processes.

Asunto(s)

Proteínas Quinasas Dependientes de Calcio-Calmodulina/fisiología , Inflamación/enzimología , Proteínas Quinasas Activadas por Mitógenos , Morfogénesis/fisiología , Transducción de Señal/fisiología , Animales , Embrión de Mamíferos/enzimología , Embrión de Mamíferos/fisiología , Embrión no Mamífero/enzimología , Embrión no Mamífero/fisiología , Humanos , Inflamación/metabolismo , Inflamación/fisiopatología , Proteínas Quinasas JNK Activadas por Mitógenos

RESUMEN

The initiation of mesoderm differentiation in the Drosophila embryo requires the gene products of twist and snail. In either mutant, the ventral cell invagination during gastrulation is blocked and no mesoderm-derived tissue is formed. One of the functions of Snail is to repress neuroectodermal genes and restrict their expressions to the lateral regions. The derepression of the neuroectodermal genes into the ventral region in snail mutant is a possible cause of defects in gastrulation and in mesoderm differentiation. To investigate such possibility, we analysed a series of snail mutant alleles. We found that different neuroectodermal genes respond differently in various snail mutant background. Due to the differential response of target genes, one of the mutant alleles, V2, that has reduced Snail function showed an intermediate phenotype. In V2 embryos, neuroectodermal genes, such as single-minded and rhomboid, are derepressed while ventral invagination proceeds normally. However, the differentiation of these invaginated cells into mesodermal lineage is disrupted. The results suggest that the establishment of mesodermal cell fate requires the proper restriction of neuroectodermal genes, while the ventral cell movement is independent of the expression patterns of these genes. Together with the data showing that the expression of some ventral genes disappear in snail mutants, we propose that Snail may repress or activate another set of target genes that are required specifically for gastrulation.

Asunto(s)

Proteínas de Unión al ADN/genética , Drosophila melanogaster/embriología , Drosophila melanogaster/genética , Gástrula/fisiología , Regulación del Desarrollo de la Expresión Génica , Factores de Transcripción , Secuencia de Aminoácidos , Animales , Diferenciación Celular , Cartilla de ADN , Proteínas de Unión al ADN/biosíntesis , Proteínas de Unión al ADN/química , Proteínas de Drosophila , Ectodermo/citología , Ectodermo/fisiología , Embrión no Mamífero/fisiología , Gástrula/citología , Genes de Insecto , Mesodermo/citología , Mesodermo/fisiología , Ratones , Datos de Secuencia Molecular , Mutación , Sistema Nervioso/citología , Sistema Nervioso/embriología , Proteínas Nucleares/biosíntesis , Proteínas Nucleares/genética , Reacción en Cadena de la Polimerasa , Alineación de Secuencia , Homología de Secuencia de Aminoácido , Factores de Transcripción de la Familia Snail , Proteína 1 Relacionada con Twist , Dedos de Zinc

RESUMEN

Patterning of the Drosophila embryo requires not only the proper activation of determinants at specific times, but also their restriction to specific places. Recent studies on transcriptional repressors show how they delimit the gene expression patterns to ensure normal development.

Asunto(s)

Proteínas de Drosophila , Drosophila/embriología , Embrión no Mamífero/fisiología , Proteínas Represoras/biosíntesis , Factores de Transcripción , Animales , Drosophila/genética , Inducción Embrionaria , Regulación del Desarrollo de la Expresión Génica , Genes de Insecto , Proteínas Nucleares/biosíntesis , Fosfoproteínas/biosíntesis

RESUMEN

The Drosophila MAP kinase DJNK is a homolog of the mammalian c-Jun amino-terminal kinase (JNK). Mutations in the DJNK gene correspond to the complementation group basket. DJNK is phosphorylated and activated by the Drosophila MAP kinase kinase HEP. Substrates of DJNK include the transcription factor DJun. DJNK participates in multiple physiological processes. Exposure to endotoxic lipopolysaccharide initiates an insect immune response and leads to DJNK activation. In addition, embryos lacking DJNK are defective in dorsal closure, a process in which the lateral epithelial cells migrate over the embryo and join at the dorsal midline. These data demonstrate that the DJNK signal transduction pathway mediates an immune response and morphogenesis in vivo.

Asunto(s)

Proteínas de Drosophila , Drosophila/embriología , Quinasas de Proteína Quinasa Activadas por Mitógenos/metabolismo , Proteínas Quinasas/metabolismo , Transducción de Señal , Alelos , Secuencia de Aminoácidos , Animales , Secuencia de Bases , ADN Complementario , Drosophila/inmunología , Drosophila/metabolismo , Regulación del Desarrollo de la Expresión Génica , Regulación Enzimológica de la Expresión Génica , Quinasas de Proteína Quinasa Activadas por Mitógenos/genética , Datos de Secuencia Molecular , Morfogénesis , Fenotipo , Fosforilación , Proteínas Quinasas/genética , Homología de Secuencia de Aminoácido , Especificidad por Sustrato

RESUMEN

A new member of the Rel family of transcription factors, the dorsal-related immunity factor, Dif, was recently cloned and suggested to be involved in regulating the immune response in Drosophila. Despite its classification as a Rel family member, the Dif cDNA-encoded product has not been proven previously to be a transcription factor. We now present evidence that the Dif gene product trans-activates the Drosophila Cecropin A1 gene in co-transfection assays. The transactivation requires a 40 bp upstream element including an insect kappa B-like motif. A dimer of the kappa B-like motif 5'-GGGGATTTTT inserted into a minimal promoter conferred high levels of reporter gene expression by Dif, while a multimer of several mutated versions of this motif was not activated, demonstrating the sequence specificity of Dif. Full trans-activation by Dif requires the C-terminal part of the protein. The morphogen dorsal (dl) can also activate the Cecropin A1 promoter, but to a lesser extent and in a less sequence-specific manner than Dif. Simultaneous overexpression of Dif and dl in co-transfection assays revealed that dl possesses a dominant negative effect on Dif transactivation. This study establishes that Dif is a sequence-specific transcription factor and is probably a key activator of the immune response in Drosophila.

Asunto(s)

Proteínas de Unión al ADN/genética , Proteínas de Drosophila , Drosophila/genética , Genes de Insecto/genética , Hormonas de Insectos/genética , Factores de Transcripción , Activación Transcripcional , Animales , Secuencia de Bases , Células Cultivadas , Proteínas de Unión al ADN/biosíntesis , Drosophila/metabolismo , Retroalimentación , Genes Reporteros , Hemocitos/metabolismo , Hormonas de Insectos/biosíntesis , Larva/genética , Larva/metabolismo , Datos de Secuencia Molecular , Mutación , Proteínas Nucleares/biosíntesis , Proteínas Nucleares/genética , Fosfoproteínas/biosíntesis , Fosfoproteínas/genética , Regiones Promotoras Genéticas , ARN Mensajero/biosíntesis , Transfección

RESUMEN

We report the isolation and characterization of a putative angiotensin converting enzyme (ACE) in Drosophila, called Race. General interest in mammalian ACE stems from its association with high blood pressure; ACE has also been implicated in a variety of other physiological processes including the processing of neuropeptides and gut peristalsis. Mammalian ACE is a membrane associated zinc binding protease that converts angiotensin I (A I) into angiotensin II (A II). A II functions as a potent vasoconstrictor by triggering a G-coupled receptor system in the smooth muscles that line blood vessels. Drosophila Race is composed of 615 amino acid residues, and shares extensive sequence identity with mammalian ACE over its entire length (over 42% overall identity and greater than 60% similarity). Evidence is presented that Race might correspond to a target of the homeobox regulatory gene, zerknullt (zen). Soon after zen expression is restricted to the dorsal-most regions of the embryonic ectoderm, Race is activated in a coincident pattern and becomes associated with the amnioserosa during germ band elongation, shortening and heart morphogenesis. After germ band elongation, Race is also expressed in both the anterior and posterior midgut, where it persists throughout embryogenesis. Race expression is lost from the dorsal ectoderm in either zen- or dpp- mutants, although gut expression is unaffected. P-transformation assays and genetic complementation tests suggest that Race corresponds to a previously characterized lethal complementation group, 1(2)34Eb. Mutants die during larval/pupal development, and transheterozygotes for two different lethal alleles exhibit male sterility. We propose that Race might play a role in the contractions of the heart, gut, or testes and also suggest that Hox genes might be important for coordinating both developmental and physiological processes.

Asunto(s)

Drosophila/enzimología , Drosophila/genética , Peptidil-Dipeptidasa A/genética , Secuencia de Aminoácidos , Animales , Secuencia de Bases , ADN Complementario/genética , Drosophila/embriología , Proteínas de Drosophila , Regulación del Desarrollo de la Expresión Génica , Genes Homeobox , Genes de Insecto , Humanos , Masculino , Ratones , Datos de Secuencia Molecular , Peptidil-Dipeptidasa A/fisiología , Conejos , Homología de Secuencia de Aminoácido , Especificidad de la Especie

RESUMEN

Dorsoventral patterning in Drosophila requires the Dorsal morphogen to act as both an activator and a repressor of transcription: an HMG1-like protein may serve to switch Dorsal from one to the other.

Asunto(s)

Proteínas de Drosophila , Drosophila/genética , Proteínas Nucleares/fisiología , Fosfoproteínas/fisiología , Proteínas Represoras/fisiología , Transactivadores/fisiología , Factores de Transcripción , Transcripción Genética/fisiología , Animales , ADN/metabolismo , Drosophila/embriología , Regulación del Desarrollo de la Expresión Génica , Proteínas del Grupo de Alta Movilidad/fisiología , Humanos

RESUMEN

In Drosophila, ventral furrow formation and mesoderm differentiation are initiated by two regulatory genes, twist (twi) and snail (sna). Both genes are evolutionarily conserved and have also been implicated in vertebrate gastrulation. Evidence is presented that sna is sufficient to initiate the invagination of the ventral-most embryonic cells in the absence of twi+ gene activity. The invaginated cells fail to express mesoderm regulatory genes, suggesting that ventral furrow formation can be uncoupled from mesoderm differentiation. Despite the previous demonstration that sna functions as a sequence-specific transcriptional repressor, low levels of sna that fail to repress neuroectoderm determinants in the presumptive mesoderm are nonetheless able to promote invagination. Cells that possess an ambiguous developmental identity can initiate the invagination process, providing further evidence that ventral furrow formation need not be linked to mesoderm differentiation.

Asunto(s)

Proteínas de Unión al ADN/metabolismo , Drosophila/embriología , Gástrula/fisiología , Mesodermo/fisiología , Proteínas Nucleares/metabolismo , Factores de Transcripción , Animales , Diferenciación Celular/genética , Diferenciación Celular/fisiología , ADN Recombinante , Proteínas de Unión al ADN/genética , Drosophila/genética , Proteínas de Drosophila , Ectodermo/fisiología , Femenino , Regulación de la Expresión Génica , Genes de Insecto , Masculino , Modelos Biológicos , Tejido Nervioso/embriología , Proteínas Nucleares/genética , Factores de Transcripción de la Familia Snail , Proteína 1 Relacionada con Twist

RESUMEN

Insects resist bacterial infections through the induction of both cellular and humoral immune responses. The cellular response involves the mobilization of hemocytes, whereas the humoral response utilizes antibacterial peptides that are synthesized in the fat bodies and secreted into the circulating hemolymph. Recent studies suggest that the induction of the humoral response involves Rel-containing regulatory proteins, Dif and dorsal, which are related to mammalian NF-kappa B. These regulatory proteins function as sequence-specific transcription factors that induce the expression of immunity genes, including cecropin and diptericin. In mammals, NF-kappa B has been implicated in both lymphocyte differentiation and the acute-phase response. The finding that insect and mammalian immunity involve related transcription factors offers the promise that genetic studies in Drosophila might lead to the identification of novel components mediating mammalian immunity.

Asunto(s)

Drosophila/genética , Drosophila/inmunología , Animales , Clonación Molecular , Femenino , Genes de Insecto , Masculino , Biología Molecular , Mutación , Transducción de Señal , Factores de Transcripción/genética