Analysis of new molecular mechanism in transcriptional regulation using Drosophila

转基因果蝇启动子分析表明，EDG 84 A基因转录起始位点140和100 bp处的几个保守序列和DHR 3结合位点对EDG 84 A基因的高效表达具有重要意义。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-F1的表达时间方面起着重要作用，FTZ-F1决定EDG 84 A基因的表达时间。本研究通过检测白色基因的表达，分析了携带EDG 84 A启动子-LacZ融合基因或携带EDG 78 E启动子-LacZ融合基因的转基因在新建立的转基因果蝇品系中插入位置的影响。在携带EDG 84 A启动子-LacZ融合基因的果蝇中，85%的品系显示出白色基因的配对依赖性激活，而其余15%的品系没有显示出这种激活。只有18%的已建立的携带EDG 78 E启动子的株系显示出白色基因的配对依赖性激活，82%的株系没有显示出这种激活。EDG 84 A启动子序列增强配对依赖性激活，而EDG 78 E启动子基本上不具有这种作用，和（2）在基因组中以相对高的效率存在配对依赖性基因激活的增强和抑制区域。

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.