RESUMO
The pre-cellular Drosophila embryo contains 10 well characterized sequence-specific transcriptional repressors, which represent a broad spectrum of DNA-binding proteins. Previous studies have shown that two of the repressors, Hairy and Dorsal, recruit a common co-repressor protein, Groucho. Here we present evidence that three different repressors, Knirps, Krüppel and Snail, recruit a different co-repressor, dCtBP. Mutant embryos containing diminished levels of maternal dCtBP products exhibit both segmentation and dorsoventral patterning defects, which can be attributed to loss of Krüppel, Knirps and Snail activity. In contrast, the Dorsal and Hairy repressors retain at least some activity in dCtBP mutant embryos. dCtBP interacts with Krüppel, Knirps and Snail through a related sequence motif, PXDLSXK/H. This motif is essential for the repression activity of these proteins in transgenic embryos. We propose that dCtBP represents a major form of transcriptional repression in development, and that the Groucho and dCtBP co-repressors mediate separate pathways of repression.
Assuntos
Proteínas de Ligação a DNA/metabolismo , Proteínas de Drosophila , Proteínas de Insetos/metabolismo , Fosfoproteínas/metabolismo , Proteínas Repressoras/metabolismo , Fatores de Transcrição/metabolismo , Oxirredutases do Álcool , Animais , Fatores de Transcrição Hélice-Alça-Hélice Básicos , Sítios de Ligação , Padronização Corporal , Fase de Clivagem do Zigoto , Proteínas de Ligação a DNA/genética , Proteínas de Ligação a DNA/fisiologia , Drosophila/embriologia , Drosophila/genética , Feminino , Regulação da Expressão Gênica no Desenvolvimento , Proteínas de Insetos/genética , Fatores de Transcrição Kruppel-Like , Masculino , Proteínas Nucleares/genética , Fosfoproteínas/genética , Fosfoproteínas/fisiologia , Proteínas Repressoras/genética , Fatores de Transcrição da Família Snail , Relação Estrutura-Atividade , Fatores de Transcrição/genética , TransgenesRESUMO
Microextraction and capillary-column gas chromatography techniques are applied to plant discharge streams for repetitive wastewater discharge permit analyses. This combination allows the analyst to reduce sample preparation since microextraction replaces both purge-and-trap for volatiles and microextraction for semi-volatiles. An additional advantage is the elimination of a concentration step, which is often a major contributor to low method recoveries. The overall procedure is shown to be more precise than purge-and-trap but slightly less precise than conventional extraction. The results of each method are shown to be equivalent.