Analysis of new molecular mechanism in transcriptional regulation using Drosophila

转基因果蝇启动子实验表明，黑胃果蝇与相关香料之间的一些保守序列和分别位于EDG84A基因转录起始位点140 bp和100 bp的DHR3结合位点对EDG84A基因的高水平表达具有重要意义。此外，我们发现蜕皮激素诱导的转录抑制因子Blimp-1在限制转录因子FTZ-Fl的表达时间方面发挥重要作用，FTZ-Fl决定了EDG84A基因的表达时间。这些发现和以往的研究结果表明，EDG84A基因的时空表达受多种转录因子的复杂机制控制。通过检测眼睛颜色表示的白色基因的表达，分析了携带EDG84A启动子-LacZ融合基因或EDG78E启动子-LacZ融合基因的转基因基因在新建立的转基因蝇系中插入位置的影响。在携带EDG84A启动子- lacz融合基因的果蝇中，85%的株系表现出白色基因的配对依赖激活，其余15%的株系没有表现出这种激活。另一方面，携带EDG78E启动子的株系中，只有18%的株系表现出白色基因的配对依赖激活，82%的株系没有表现出这种激活。这些结果表明：(1)EDG84A启动子序列增强配对依赖激活，而EDG78E启动子基本不具有这种作用；(2)基因组内存在较高效率的配对依赖基因激活增强区和抑制区。

Transgenic fly promoter assay revealed that several conserved sequences between Drosophila melanogaster and related spices and DHR3 binding site which locates 140 and 100 bp, respectively, from the transcriptional start site of the EDG84A gene are important for high level expression of the EDG84A gene. Furthermore, we showed that ecdysone-inducible transcriptional repressor Blimp-1 plays an important role to restrict the expression timing of the transcription factor FTZ-Fl which determines expression timing of the EDG84A gene. These findings and previous results indicate that temporal and spatial expression of the EDG84A gene is controlled by complicated mechanism including several transcription factors.Effects of insertion positions of transgenes carrying the EDG84A promoter-LacZ fusion gene or the EDG78E promoter- LacZ fusion gene in newly established transgenic fly lines were analyzed by detecting expression of the white gene indicated by eye color. In the fly carrying the EDG84A promoter-LacZ fusion gene, 85% of the lines showed the pairing dependent activation of the white gene and the rest of the 15% did not show it. On the other hand, only 18% of the established lines carrying the EDG78E promoter showed the pairing dependent activation of the white gene and 82% did not show it. These results suggest that (1) the EDG84A promoter sequence enhances the pairing dependent activation and the EDG78E promoter basically dose not have such effect, and (2) enhancing and suppressing regions for the pairing dependent gene activation are present within the genome in relatively high efficiency.