RESUMO
The paper first analyzes the effect of backlight unit for liquid crystal displays on the respect of image quality and power consumption. A spatially and temporally addressable backlight is required in the future liquid crystal displays which have lower power consumption and higher image quality. Compared to the currently used light emitting diode backlight, the simulation results indicate that a rectangular-shaped backlight has better performances on the respect of reducing power consumption and improving image quality. A backlight cell based on the field emission is manufactured and studied. It uses a mixture of multi-wall carbon nanotubes and tetrapod-like zinc oxide nanostructures as the cathode and applies spin-coating process for fabrication. The experiment shows that such field emission backlight unit has a low turn-on field which enables a high backlight luminance at acceptable driving voltage. Besides, this mixture cathode helps to improve the uniformity of field emission in both spatial and temporal domain which is important for the application of backlight unit.
RESUMO
The rat protease nexin-1 (PN-1) promoter contains a GCGGGGGCG binding site for the transcription factors Krox-24, Krox-20 and NGFI-C. Mutations of this site abolished binding of Krox-24 in vitro. The wildtype protease nexin-1 promoter expressed beta-galactosidase similarity to the expression of protease nexin-1 mRNA. When the function of this Krox site was tested in vivo using transgenic F0 embryos, mutation had two opposite effects. beta-Galactosidase expression increased in cartilage and heart at both stages E11.5 and E13.5, but was abolished in nerves of the central and peripheral nervous system at stage E13.5. These results suggest that Krox factors are among the important transcription factors regulating protease nexin-1 expression and thereby intracellular proteolytic activity in embryonic heart, cartilage and parts of the nervous system.
Assuntos
Proteínas de Transporte/genética , Proteínas de Ligação a DNA/metabolismo , Regulação da Expressão Gênica , Proteínas Imediatamente Precoces , Inibidores de Serina Proteinase/genética , Fatores de Transcrição/metabolismo , Precursor de Proteína beta-Amiloide , Animais , Sequência de Bases , Sítios de Ligação , Proteínas de Transporte/metabolismo , Cartilagem/metabolismo , Proteína 1 de Resposta de Crescimento Precoce , Proteína 2 de Resposta de Crescimento Precoce , Camundongos , Camundongos Transgênicos , Dados de Sequência Molecular , Mutagênese Sítio-Dirigida , Miocárdio/metabolismo , Sistema Nervoso/metabolismo , Regiões Promotoras Genéticas/genética , Nexinas de Proteases , Ratos , Receptores de Superfície Celular , Inibidores de Serina Proteinase/metabolismo , Fatores de Tempo , Fatores de Transcrição/química , Transfecção , Células Tumorais CultivadasRESUMO
In a recent gene-trap screen, we identified the gene coding for Epidermal Bullous Pemphigoid Antigen 1 (BPAG1) as a putative transcriptional target of Engrailed and of other homeoproteins with a glutamine in position 50 of their homeodomain. We now show that the nuclear addressing of the homeodomains of Engrailed (EnHD) and Antennapedia (AntpHD) upregulates BPAG1e transcription in immortalized human keratinocytes (GMA24FIA) expressing En1. This upregulation is not observed with AntpHD-Q50A, a variant of AntpHD in which a single mutation abolishes its high-affinity binding to target DNA, thus strongly suggesting that BPAG1e upregulation homeodomains reflects their specific recognition of homeoprotein-binding sites in the BPAG1e locus. This is further confirmed by DNase I footprinting and electrophoretic mobility shift assays that reveal, within the cloned BPAG1e promoter, several sites of direct interaction with EnHD and Engrailed. Co-transfection experiments in GMA24FIA human keratinocytes, COS-7 simian fibroblasts, and CHP-100 human neuroepithelial cells show that Engrailed, Hoxa-5, and Hoxc-8 regulate BPAG1e promoter activity and that this regulation is context-dependent. Finally, using a mouse line with LacZ inserted within the En1 locus, we identify the keratinocytes of the ventral paws, including the epithelial cells of the eccrine tubules, as a strong site of En1 expression throughout adulthood. We therefore propose that BPAG1e, a 230 kDa keratin-binding protein expressed in keratinocytes and participating in the maintenance of hemidesmosomes at the dermis-epidermis border, is directly regulated by homeoprotein transcription factors.
Assuntos
Autoantígenos/biossíntese , Proteínas de Transporte , Colágeno , Proteínas do Citoesqueleto , Proteínas de Homeodomínio/fisiologia , Proteínas do Tecido Nervoso , Colágenos não Fibrilares , Proteínas Nucleares , Penfigoide Bolhoso/imunologia , Fatores de Transcrição/fisiologia , Animais , Proteína do Homeodomínio de Antennapedia , Autoantígenos/genética , Sequência de Bases , Células Cultivadas , Desmossomos/metabolismo , Distonina , Regulação da Expressão Gênica , Humanos , Queratinócitos/metabolismo , Camundongos , Dados de Sequência Molecular , Regiões Promotoras Genéticas , Colágeno Tipo XVIIRESUMO
The first three exons and the promoter of rat glia-derived nexin, also called protease nexin-1 (GDN/PN-1), have been identified through analysis of rat genomic clones. A 1.6 kilobase (kb) fragment containing 105 base pairs of the first exon and 5'-flanking sequences was sequenced. The 5'-flanking sequence and the first exon were found to be GC-rich, indicating that the 5' region of the rat GDN/PN-1 gene resides within a CpG island. A TATA box-like sequence, but no CAAT box, was found. The rat GDN/PN-1 promoter contains five SP1 consensus sites, four consensus sites for the MyoD1 transcription factor, and one binding site for the transcription factors NGFI-A, NGFI-C, Krox-20, and Wilms tumor factor. The presence of these consensus sequences is consistent with the known expression pattern of GDN/PN-1. Primer extension and RNase protection assays identified one transcriptional start site. The 1.6 kb promoter fragment cloned in a reporter plasmid was found to induce firefly luciferase expression in a cell-specific manner. A positive regulatory element is localized in the region -1545 to -389. In vitro CpG methylation blocked transcription from the GDN/PN-1 promoter in rat hepatoma cells but not in C6 rat glioma cells.