Study on the Transcription Factor that regulates Placenta-Specific Expression

我们已经找到了一个新的顺式元件，滋养细胞特异性元件2 （TSE2）位于人类芳香酶基因的胎盘特异性增强子中，该基因决定了其组织特异性表达。在最小增强子区，一个类似于滋养细胞特异性元件（TSE）的元件也存在，最初被描述为人类绒毛膜促性腺激素α亚基基因（Yamada， K., et al. 1995 J.Biol.Chem.）。270年,25064 - 25069)。TSE和TSE2的共同存在是指导由异源胸苷激酶启动子驱动的滋养细胞特异性表达所必需的。利用酵母单杂交系统，以TSE2为报告序列，从人胎盘cDNA文库中分离到一个2562碱基对的cDNA克隆，该克隆编码一个436个氨基酸的与TSE2结合的蛋白。该蛋白被发现与hGCMa相同，hGCMa是果蝇GCM（胶质细胞缺失）蛋白的哺乳动物同源物。hGCMa的表达仅限于胎盘。在Sf - 21细胞中表达的蛋白也与瘦素启动子中的PLE1结合，以及其他一些报道赋予胎盘特异性表达的顺式元件，这表明hGCMa是一种胎盘特异性转录调节剂，可能参与了多个胎盘特异性基因的表达。（Yamada， K.et al ., 1999）我们还分析了该基因的基因组组织、染色体定位和完整的22kb DNA序列。它包含6个外显子和5个内含子，编码2.8 kb的cDNA。人类和小鼠的整体基因组组织是相似的。在人类基因的5'侧区发现了转录因子如GATA、Oct-1和bHLH蛋白的几个潜在结合位点。GCM蛋白结合的DNA基序存在于5'侧区，与小鼠基因高度同源。利用荧光原位杂交技术将该基因定位到6号染色体上。（Yamada, k. et al, Biochem biophysres comm2000 278, 134-139）

We have located a new cis-element, trophoblast-specific element 2 (TSE2) is located in the placenta-specific enhancer of the human aromatase gene that dictates its tissue-specific expression. In the minimum enhancer region, an element similar to the trophoblast-specific element (TSE), originally described for the human chorionic gonadotropin alpha-subunit gene, also exists (Yamada, K., et al. 1995 J.Biol.Chem.270, 25064-25069). The co-presence of TSE and TSE2 is required to direct trophoblast-specific expression driven by a heterologous thymidine kinase promoter.A 2562-base pair cDNA clone encoding a 436-amino acid protein that binds to TSE2 was isolated from a human placental cDNA library using a yeast one-hybrid system with the TSE2 as a reporter sequence. The protein was revealed to be identical to hGCMa, a mammalian homologue of the Drosophila GCM (glia cells missing) protein.Expression of hGCMa is restricted to the placenta. The protein expressed in Sf 21 cells also binds to PLE1 in the leptin promoter among other cis-elements reported to confer placenta-specific expression, suggesting that hGCMa is a placenta-specific transcription regulator, possibly involved in the expression of multipleplacenta-specific genes.(Yamada, K.et al, 1999 J.Biol.Chem.274 : 32279-86)We also analyzed the genomic organization, chromosomal localization, and the complete 22 kb DNA sequence of the gene. It contains six exons and five introns, encoding a 2.8 kb cDNA.Overall genomic organization is similar for the human and mouse. Several potential binding sites for transcription factors like GATA, Oct-1, and bHLH proteins were found in the 5'-flanking region of the human gene. A DNA motif for GCM protein binding exists in the 5'-flanking region that is highly homologous with that of the mouse gene. The location of this gene was mapped to chromosome 6 using fluorescence in situ hybridization.(Yamada, k. et al, Biochem Biophys Res Commun 2000 278, 134-139)