Specificity of DNA-binding by the FAX-1 and NHR-67 nuclear receptors of Caenorhabditis elegans is partially mediated via a subclass-specific P-box residue

<p>Abstract</p> <p>Background</p> <p>The nuclear receptors of the NR2E class play important roles in pattern formation and nervous system development. Based on a phylogenetic analysis of DNA-binding domains, we define two conserved groups of orthologous NR2E genes: the NR2E1 subclass, which includes <it>C. elegans nhr-67, Drosophila tailless </it>and <it>dissatisfaction</it>, and vertebrate Tlx (NR2E2, NR2E4, NR2E1), and the NR2E3 subclass, which includes <it>C. elegans fax-1 </it>and vertebrate PNR (NR2E5, NR2E3). PNR and Tll nuclear receptors have been shown to bind the hexamer half-site AAGTCA, instead of the hexamer AGGTCA recognized by most other nuclear receptors, suggesting unique DNA-binding properties for NR2E class members.</p> <p>Results</p> <p>We show that NR2E3 subclass member FAX-1, unlike NHR-67 and other NR2E1 subclass members, binds to hexamer half-sites with relaxed specificity: it will bind hexamers with the sequence ANGTCA, although it prefers a purine to a pyrimidine at the second position. We use site-directed mutagenesis to demonstrate that the difference between FAX-1 and NHR-67 binding preference is partially mediated by a conserved subclass-specific asparagine or aspartate residue at position 19 of the DNA-binding domain. This amino acid position is part of the "P box" that plays a critical role in defining binding site specificity and has been shown to make hydrogen-bond contacts to the second position of the hexamer in co-crystal structures for other nuclear receptors. The relaxed specificity allows FAX-1 to bind a much larger repertoire of half-sites than NHR-67. While NR2E1 class proteins bind both monomeric and dimeric sites, the NR2E3 class proteins bind only dimeric sites. The presence of a single strong site adjacent to a very weak site allows dimeric FAX-1 binding, further increasing the number of dimeric binding sites to which FAX-1 may bind <it>in vivo</it>.</p> <p>Conclusion</p> <p>These findings identify subclass-specific DNA-binding specificities and dimerization properties for the NR2E1 and NR2E3 subclasses. For the NR2E1 protein NHR-67, Asp-19 permits binding to AAGTCA half-sites, while Asn-19 permits binding to AGGTCA half-sites. The apparent conservation of DNA-binding properties between vertebrate and nematode NR2E receptors allows for the possibility of evolutionarily-conserved regulatory patterns.</p

Transcriptional Control of Steroid Biosynthesis Genes in the Drosophila Prothoracic Gland by Ventral Veins Lacking and Knirps.

Specialized endocrine cells produce and release steroid hormones that govern development, metabolism and reproduction. In order to synthesize steroids, all the genes in the biosynthetic pathway must be coordinately turned on in steroidogenic cells. In Drosophila, the steroid producing endocrine cells are located in the prothoracic gland (PG) that releases the steroid hormone ecdysone. The transcriptional regulatory network that specifies the unique PG specific expression pattern of the ecdysone biosynthetic genes remains unknown. Here, we show that two transcription factors, the POU-domain Ventral veins lacking (Vvl) and the nuclear receptor Knirps (Kni), have essential roles in the PG during larval development. Vvl is highly expressed in the PG during embryogenesis and is enriched in the gland during larval development, suggesting that Vvl might function as a master transcriptional regulator in this tissue. Vvl and Kni bind to PG specific cis-regulatory elements that are required for expression of the ecdysone biosynthetic genes. Knock down of either vvl or kni in the PG results in a larval developmental arrest due to failure in ecdysone production. Furthermore, Vvl and Kni are also required for maintenance of TOR/S6K and prothoracicotropic hormone (PTTH) signaling in the PG, two major pathways that control ecdysone biosynthesis and PG cell growth. We also show that the transcriptional regulator, Molting defective (Mld), controls early biosynthetic pathway steps. Our data show that Vvl and Kni directly regulate ecdysone biosynthesis by transcriptional control of biosynthetic gene expression and indirectly by affecting PTTH and TOR/S6K signaling. This provides new insight into the regulatory network of transcription factors involved in the coordinated regulation of steroidogenic cell specific transcription, and identifies a new function of Vvl and Knirps in endocrine cells during post-embryonic development

1394AP: A protocol for deterministic industrial communication via IEEE 1394

In this contribution we present an application layer called 1394AP (1394 Automation Protocol) for the industrial use of the IEEE 1394 "FireWire" standard which is favorable for factory automation because of its inherently deterministic network behavior. Starting from an analysis of industrial communication requirements and an overview of the principles of IEEE 1394, it will be shown that also other advantages make IEEE 1394 a promising network for industrial use. The following sections describe the 1394AP protocol in detail and explain how to implement the necessary hardware and software based on general purpose architecture of an IEEE 1394 embedded node. The paper will conclude with an outlook on the next steps in the ongoing specification process of 1394AP

Introdução - História social, capitalismo global e mundos do trabalho: entrelaçamentos e convergências historiográficas

O objetivo primordial desta coletânea é apresentar ao público um conjunto de investigações recentes em história social, produzidas no Brasil, que se lançam à observação de determinados contextos na África e nas Américas. Os capítulos a seguir examinam, sob ângulos diversos, uma variedade de temas e objetos situados em espaços e temporalidades inscritos nos quadros do capitalismo global.info:eu-repo/semantics/publishedVersio

Liberdades fraturadas: diálogos cruzados em história social

O que significava a liberdade para aqueles que viveram a escravidão, sua abolição e o período subsequente, que estiveram sob o jugo do colonialismo e puderam conhecer a independência? Os artigos que compõem esta coletânea, escritos por jovens pesquisadores da história social, buscam respostas para esta questão examinando diferentes tempos e lugares. Na África e nas Américas, o mundo que se constituiu depois do domínio senhorial e colonial manteve várias formas de coerção ao trabalho e impôs muitas limitações à tão sonhada liberdade. Do século XIX aos nossos dias, a reprodução das desigualdades sociais e a restrição de direitos tolheram as possibilidades daqueles que queriam ser livres. Colhidas em fontes diversas, essas experiências fraturadas de liberdade oferecem aqui matéria para muitas reflexões: sobre a história, sobre a pesquisa histórica e sobre a vida contemporânea. Um livro para ler e que faz pensar.info:eu-repo/semantics/publishedVersio

MOEMS laser projector for handheld devices featuring motion compensation

Laser projection has been realized using a 2d micromechanical scanner mirror. For handheld devices it is advantageous to compensate motion. This can be realized using inertial sensors for motion detection and the implementation of a compensation algorithms. The projector must provide sufficient dynamic range for the compensation. A demo system was realized and tested succesfully