Regulation of per and cry Genes Reveals a Central Role for the D-Box Enhancer in Light-Dependent Gene Expression

Light serves as a key environmental signal for synchronizing the circadian clock with the day night cycle. The zebrafish represents an attractive model for exploring how light influences the vertebrate clock mechanism. Direct illumination of most fish tissues and cell lines induces expression of a broad range of genes including DNA repair, stress response and key clock genes. We have previously identified D- and E-box elements within the promoter of the zebrafish per2 gene that together direct light-induced gene expression. However, is the combined regulation by E- and D-boxes a general feature for all light-induced gene expression? We have tackled this question by examining the regulation of additional light-inducible genes. Our results demonstrate that with the exception of per2, all other genes tested are not induced by light upon blocking of de novo protein synthesis. We reveal that a single D-box serves as the principal light responsive element within the cry1a promoter. Furthermore, upon inhibition of protein synthesis D-box mediated gene expression is abolished while the E-box confers light driven activation as observed in the per2 gene. Given the existence of different photoreceptors in fish cells, our results implicate the D-box enhancer as a general convergence point for light driven signaling

PRL3-DDX21 transcriptional control of endolysosomal genes restricts melanocyte stem cell differentiation

Melanocytes, replenished throughout life by melanocyte stem cells (MSCs), play a critical role in pigmentation and melanoma. Here, we reveal a function for the metastasis-associated phosphatase of regenerating liver 3 (PRL3) in MSC regeneration. We show that PRL3 binds to the RNA helicase DDX21, thereby restricting productive transcription by RNAPII at master transcription factor (MITF)-regulated endolysosomal vesicle genes. In zebrafish, this mechanism controls premature melanoblast expansion and differentiation from MSCs. In melanoma patients, restricted transcription of this endolysosomal vesicle pathway is a hallmark of PRL3-high melanomas. Our work presents the conceptual advance that PRL3-mediated control of transcriptional elongation is a differentiation checkpoint mechanism for activated MSCs and has clinical relevance for the activity of PRL3 in regenerating tissue and cancer

Temperature Regulates Transcription in the Zebrafish Circadian Clock

It has been well-documented that temperature influences key aspects of the circadian clock. Temperature cycles entrain the clock, while the period length of the circadian cycle is adjusted so that it remains relatively constant over a wide range of temperatures (temperature compensation). In vertebrates, the molecular basis of these properties is poorly understood. Here, using the zebrafish as an ectothermic model, we demonstrate first that in the absence of light, exposure of embryos and primary cell lines to temperature cycles entrains circadian rhythms of clock gene expression. Temperature steps drive changes in the basal expression of certain clock genes in a gene-specific manner, a mechanism potentially contributing to entrainment. In the case of the per4 gene, while E-box promoter elements mediate circadian clock regulation, they do not direct the temperature-driven changes in transcription. Second, by studying E-box-regulated transcription as a reporter of the core clock mechanism, we reveal that the zebrafish clock is temperature-compensated. In addition, temperature strongly influences the amplitude of circadian transcriptional rhythms during and following entrainment by light–dark cycles, a property that could confer temperature compensation. Finally, we show temperature-dependent changes in the expression levels, phosphorylation, and function of the clock protein, CLK. This suggests a mechanism that could account for changes in the amplitude of the E-box-directed rhythm. Together, our results imply that several key transcriptional regulatory elements at the core of the zebrafish clock respond to temperature

Stress from Nucleotide Depletion Activates the Transcriptional Regulator HEXIM1 to Suppress Melanoma

Studying cancer metabolism gives insight into tumorigenic survival mechanisms and susceptibilities. In melanoma, we identify HEXIM1, a transcription elongation regulator, as a melanoma tumor suppressor that responds to nucleotide stress. HEXIM1 expression is low in melanoma. Its overexpression in a zebrafish melanoma model suppresses cancer formation, while its inactivation accelerates tumor onset in vivo. Knockdown of HEXIM1 rescues zebrafish neural crest defects and human melanoma proliferation defects that arise from nucleotide depletion. Under nucleotide stress, HEXIM1 is induced to form an inhibitory complex with P-TEFb, the kinase that initiates transcription elongation, to inhibit elongation at tumorigenic genes. The resulting alteration in gene expression also causes anti-tumorigenic RNAs to bind to and be stabilized by HEXIM1. HEXIM1 plays an important role in inhibiting cancer cell-specific gene transcription while also facilitating anti-cancer gene expression. Our study reveals an important role for HEXIM1 in coupling nucleotide metabolism with transcriptional regulation in melanoma

Kita Driven Expression of Oncogenic HRAS Leads to Early Onset and Highly Penetrant Melanoma in Zebrafish

Melanoma is the most aggressive and lethal form of skin cancer. Because of the increasing incidence and high lethality of melanoma, animal models for continuously observing melanoma formation and progression as well as for testing pharmacological agents are needed.Using the combinatorial Gal4-UAS system, we have developed a zebrafish transgenic line that expresses oncogenic HRAS under the kita promoter. Already at 3 days transgenic kita-GFP-RAS larvae show a hyper-pigmentation phenotype as earliest evidence of abnormal melanocyte growth. By 2-4 weeks, masses of transformed melanocytes form in the tail stalk of the majority of kita-GFP-RAS transgenic fish. The adult tumors evident between 1-3 months of age faithfully reproduce the immunological, histological and molecular phenotypes of human melanoma, but on a condensed time-line. Furthermore, they show transplantability, dependence on mitfa expression and do not require additional mutations in tumor suppressors. In contrast to kita expressing melanocyte progenitors that efficiently develop melanoma, mitfa expressing progenitors in a second Gal4-driver line were 4 times less efficient in developing melanoma during the three months observation period.This indicates that zebrafish kita promoter is a powerful tool for driving oncogene expression in the right cells and at the right level to induce early onset melanoma in the presence of tumor suppressors. Thus our zebrafish model provides a link between kita expressing melanocyte progenitors and melanoma and offers the advantage of a larval phenotype suitable for large scale drug and genetic modifier screens

Live Imaging of Innate Immune Cell Sensing of Transformed Cells in Zebrafish Larvae: Parallels between Tumor Initiation and Wound Inflammation

Live imaging and genetic studies of the initial interactions between leukocytes and transformed cells in zebrafish larvae indicate an attractant role for H2O2 and suggest that blocking these early interactions reduces expansion of transformed cell clones

Contacts et acculturations en Méditerranée occidentale

La question des contacts entre les différents peuples qui bordent les rives de la Méditerranée nord occidentale est l’un des sujets phares de la recherche archéologique de ces trente dernières années. Que l’on parle d’époque archaïque et classique ou de Protohistoire et d’âge du Fer, les échanges et les processus d’acculturation de ces peuples qui entrèrent alors en contact les uns avec les autres : Grecs, Celtes, Phéniciens, Ibères, Ligures, Étrusques, ont retenu l’attention des chercheurs travaillant sur l’expansion grecque dans ces régions, sur les trafics commerciaux, sur les échanges culturels. L’œuvre de Michel Bats (Directeur de recherche honoraire du CNRS) traverse toutes ces thématiques : la présence des Phocéens et des Étrusques dans le bassin occidental de la Méditerranée, l’acculturation et les identités ethno-culturelles, les recherches sur la céramique et ses usages dans une perspective anthropologique, l’appropriation de l’écriture par les sociétés protohistoriques. Ses collègues et amis, en organisant ce colloque et en participant à ces actes, entendent lui témoigner leur amitié et leur dette intellectuelle. Ce volume réunit des articles des meilleurs spécialistes, actuels de la question - des chercheurs de toute la Méditerranée - autour des quatre grands thèmes que nous venons d’évoquer afin tout à la fois de dresser un bilan et de définir de nouvelles perspectives. Cet ouvrage présente donc aussi bien des synthèses - sur la présence grecque en Espagne, sur l’origine de l’écriture, sur les pratiques funéraires, sur les identités culturelles et ethniques - que des découvertes récentes concernant la thématique des contacts et de l’acculturation en Méditerranée nord occidentale : l’agglomération du Premier âge du Fer de La Cougourlude (Lattes, Hérault) fouillée durant l’été 2010 ; le sanctuaire hellénistique de Cumes et les fouilles récentes de Fratte en Italie ; les ateliers de potiers de Rosas en Espagne ; les dernières découvertes d’Olbia de Provence

El turismo en México. Apreciaciones sobre el turismo en espacio litoral

México es uno de los líderes del turismo internacional receptivo, con más de veinte millones de turistas ingresados por año a partir de los inicios del siglo XXI. Esta posición de privilegio se fundamenta en una variada oferta de productos turísticos, desde el clásico turismo de sol y playa en varios centros vacacionales localizados en ambas costas del país, el turismo arqueológico revalorizando el patrimonio que testimonian el devenir de avanzadas civilizaciones precolombinas; el turismo cultural que refleja la impronta de la conquista española manifiesta en sus ciudades coloniales y las obras del hombre contemporáneo, el turismo alternativo con fuerte vinculación con la naturaleza, el turismo de compras localizado a lo largo de la frontera norte, o bien el turismo de cruceros con puertos sobre las costas del Mar Caribe y Océano Pacífico. A partir de 1960 el Estado se abocó a la planificación del turismo creando centros turísticos integralmente planificados. Elaboró el primer Plan Nacional de Desarrollo Turístico y ejerció un rol central en la evolución de la actividad, buscando una respuesta favorable a su balanza comercial y paliar las deficiencias en la economía como consecuencia de aplicar una política de sustitución de importaciones. La importancia del turismo, así como la variedad de sus recursos, determinaron zonas con gran vocación turística, pero al mismo tiempo se generó una marcada dualidad territorial debido a la presencia de concentraciones y grandes vacíos poblacionales. Para abordar el tema del Turismo en México se presenta una breve descripción de los principales rasgos geográficos del país, luego se realiza una síntesis del devenir de la actividad turística, haciendo referencia a la planificación turística originada a fines de la década de los años sesenta. Se analiza la dicotomía entre centros turísticos tradicionales y centros turísticos integralmente planificados, brindando ejemplos en ambos casos. Se reflexiona sobre el accionar de los organismos oficiales de turismo que contribuyen con el desarrollo de centros turísticos y se concluye analizando la situación del turismo en la actualidad.Mexico is one of the leaders of receptive international tourism, receiving more than twenty million tourists a year since the beginning of the XXI century. This position of privilege is based on a varied offer of tourist products, from the typical sun and beach tourism in several vacation centres located on both coasts of the country, as well as archaeological tourism which aims at a reassessment of the heritage that testifies to the future of advanced pre-Columbian civilizations. Equally important is cultural tourism that reflects the mark of the Spanish conquest in its colonial cities and the Works of contemporary men; and also alternative tourism with a strong link with nature, and shopping tourism located along the northern border; and finally cruiser tourism with harbours on the coasts of the Caribbean Sea and the Pacific Ocean. From 1960 onwards the State devoted to the planning of tourism creating tourist centres planned comprehensively. It drew up the first National Plan of Tourist Development and exerted a leading role in the evolution of the activity, by searching for a favourable answer to its commercial balance and aiming at alleviating the economic problems present as a consequence of the application of a policy of substitution of imports. The importance of tourism, as well as the variety of its resources, determined areas with great tourist potential, but at the same time there was a marked territorial division generated due to the presence of concentrations and big population gaps. In order to deal with the topic of tourism in Mexico we present a brief description of the main geographical features of the country, then a synthesis of the future of tourist activity there, making reference to tourist planning originated at the end of the 1960s. The dichotomy between traditional tourist centres and those comprehensively planned was analysed, providing examples in both cases. There is a reflexion on the action of official tourism offices that contribute to the development of tourist centres and the study concludes with an analysis of the present situation of tourism.Fil: Benseny, Graciela. Universidad Nacional de Mar del Plata. Facultad de Ciencias Económicas y Sociales; Argentina