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，滋养层细胞特异性元件2（TSE 2）位于胎盘特异性增强的人芳香化酶基因，决定其组织特异性表达。在最小增强子区域中，也存在与最初描述用于人绒毛膜促性腺激素α-亚基基因的滋养层特异性元件（TSE）类似的元件（Yamada，K.，等人，1995 J.Biol.Chem.270，25064-25069）。利用酵母单杂交系统，以TSE 2为报告基因，从人胎盘cDNA文库中克隆了一个2562 bp的cDNA克隆，编码436个氨基酸的TSE 2结合蛋白。该蛋白被揭示为与hGCMa相同，hGCMa是果蝇GCM（神经胶质细胞缺失）蛋白的哺乳动物同源物。在Sf 21细胞中表达的蛋白质还结合到瘦素启动子中的PLE 1，以及其他据报道赋予胎盘特异性表达的顺式元件，这表明hGCMa是胎盘特异性转录调节因子，可能参与多个胎盘特异性基因的表达。（Yamada，K.et al，1999 J.Biol.Chem.274：32279-86）我们还分析了该基因的基因组结构、染色体定位和完整的22 kb DNA序列。它包含6个外显子和5个内含子，编码一个2.8kb的cDNA。在人基因的5 '侧翼区发现了几个转录因子如加塔、Oct-1和bHLH蛋白的潜在结合位点。GCM蛋白结合的DNA基序存在于与小鼠基因高度同源的5 '-侧翼区。利用荧光原位杂交技术将该基因定位于第6号染色体。（Yamada，k.等人，Biochem Biophys Res Commun 2000 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)