Analysis on the transcriptional regulation mechanism of aromatase gene

芳香酶广泛分布于各种性腺外组织和性腺组织中，参与多种生理功能。芳香酶在这些组织中的表达受组织特异性因子和组织依赖机制的调控。在本研究中，我们以绒毛膜癌Bewo细胞为研究对象，对芳香酶基因在转录水平的复杂调控机制进行了分析。我们在距芳香酶基因转录起始点2.8kb的上游约500个碱基对(Bp)处只观察到一个启动子。令人意外的是，该位点的启动子活性对cAMP或TPA作为芳香酶基因转录诱导剂的诱导没有反应。进一步分离了芳香酶基因5‘侧翼区的13kb片段，并对该区域的启动子进行了筛选。然而，该区域没有任何可检测到的启动子活性。然后，我们用绒毛膜癌来源的JEG-3细胞作为更适合芳香酶诱导的培养细胞。从芳香酶活性和mRNA水平观察到，JEG-3细胞表达了大量的芳香化酶，其表达受与人胎盘相同的因素的调控。用JEG-3细胞检测了芳香酶基因5‘侧翼区(13kb)的启动子活性。因此，除了上述500bp的上游位点外，还新发现了两个启动子位点。它们位于转录起始点上游约2kb和1kb处，具有启动子活性，分别具有正调控和负调控作用。然而，在JEG-3细胞中，我们也没有在芳香酶基因的这个区域发现任何cAMP或TPA反应的启动子位点。进一步的筛查目前正在进行中。

Aromatase has been known to be widely distributed in various extra-gonadal tissues as well as gonadal tissues and to take part in various physiological functions. The expression of aromatase in these tissues was regulated by tissuespecific factors and tissue-dependent mechanisms. In this study, we used Bewo cells derived from choriocarcinoma for such analyses and analyzed on these complicated regulation mechanisms in the transcription level of aromatase gene. We observed only one promoter site at the approximately 500 base pairs (bp) upstream within 2.8 kb from the transcriptional initiation site of aromatase gene. Unexpectedly, the promoter activity in this site was not responsive to the induction by CAMP or TPA as transcriptional inducers of aromatase gene. The 13 kb fragment of 5'-flanking region of aromatase gene was furhter isolated and the screening of promoter sites in the region was carried out. However, there were not any detectable promoter activities in this region. Then, we used JEG-3 cells derived from choriocarcinoma as more suitable culture cells for analysis of aromatase induction. It was observed in the levels of aromatase activity and mRNA that JEG-3 cells expressed aromatase so much and its expression was regulated by the same factors as human placenta. By using JEG-3 cells, the promoter activity of 5'-flanking region (13 kb) of aromatase gene was examined. Consequently, two promoter sites was newly found in addition to 500 bp upstream site described above. They were located at about 2 kb and 1 kb upstream from the transcriptional initiation site and had promoter activities with positive and negative regulatory actions, respectively. However, in the case of JEG-3 cells, we could not also find any CAMP- or TPA-responsive promoter sites in this region of aromatase gene. Further screening is now being in progress.