Primary structure and regulation of vegetative specific genes of Dictyostelium discoideum

We have examined the expression and structure of several genes belonging to two classes of vegetative specific genes of the simple eukaryote, Dictyostelium discoideum. In amebae grown on bacteria, deactivation of all vegetative specific genes occurred at the onset of development and very little mRNA exists by 8 to 10 hours. In contrast, when cells were grown in axenic broth, the mRNA levels remained constant until a dramatic drop occurred around 10 to 12 hours. Thus, regulation of both classes of genes during the first several hours of development is dependent upon the prior growth conditions. Analysis of genomic clones has resulted in the identification of two V genes, V1 and V18, as ribosomal protein genes. Several other V genes were not found to be ribosomal protein genes, suggesting that in Dictyostelium non-ribosomal protein genes may be coordinately regulated with the ribosomal protein genes. Finally, using deletion analysis we show that the promoters of two of the V genes are composed of a constitutive positive element(s) located upstream of sequences involved in the regulated expression of these genes and within the first 545 upstream bp for V18 and 850 bp for V14. The regions involved in regulated expression were localized between -7 and -222 for V18 and -70 and -368 for V14. The sequences conferring protein synthesis sensitivity were shown to reside between -502 and -61 of the H4 promoter.     

牛磺胆酸作用下副溶血弧菌全基因组比较转录谱的表达分析

目的利用DNA芯片技术研究副溶血弧菌对牛磺胆酸刺激反应的全局性基因转录变化概况,找出其中的表达调控变化规律,为副溶血弧菌基因转录调控网络的构建提供实验和理论依据。方法副溶血弧菌分别在正常和添加了50mmol／L牛磺胆酸的培养基中孵育至对数中期,收集菌体,提取RNA,利用全基因组DNA芯片分析比较两者基因转录变化。并应用聚类分析比较其中的变化规律。结果比较转录谱分析证实一共有255个基因的转录表达发生显著性变化,和对照组相比,上调的基因明显占主导优势。而在这些变化的基因中,关于蛋白合成和硫代谢以及谷氨酸合成相关的基因均呈现明显的转录上调变化。结论我们利用DNA芯片技术描绘出了副溶血弧菌在添加牛磺胆酸后全部基因转录水平变化的概图,并发现了蛋白合成,硫代谢和谷氨酸合成相关的基因的变化规律,这给我们下一步的转录调控网络研究提供了良好的靶标。