E BOX ELEMENTS IN CG BETA GENE TRANSCRIPTION: PLACENTA

目的：测定绒毛膜促性腺激素β 基因受E盒结合转录因子的调控。结果 适合发育和细胞特异性的基因转录是 在许多器官中受与E盒结合的转录因子调节 Motif。人绒毛膜促性腺激素β亚基的检测 5‘-侧翼DNA显示在-274(A盒)，-135处有三个E盒状基序 (B框)和相对于转录起始位置的-126(C框)。 为了研究这些元件是否在基因转录中发挥作用， A盒、B/C盒或所有三个位点都发生了突变和活性 被比作野性活动。JEG-3基因的转染 绒毛膜癌细胞显示单个E盒突变 基础转录减少约50%，但折叠诱导 CAMP(滋养层功能的标志)并不显著。 变化。所有三个E盒的突变都导致了75%的 基础转录，但不是cAMP诱导的折叠。凝胶 使用A盒进行的迁移率漂移分析显示了两个不是 针对滋养层细胞的特异性，以及与特异性的超移位分析 多种E盒结合蛋白的抗血清证明 而没有一个特定的络合物含有bHLH二聚体伙伴 E12/E47，至少有一条带包含广泛表达的 转录因子USF-1。USF-1最近的未来方向是 证实在常见的糖蛋白中结合了一个E盒样元件 激素α亚单位启动子参与转录 该基因在小鼠垂体促性腺激素肿瘤细胞中的激活。 这表明胎盘CG的表达也起到了作用，我们将 检查USF-1是否为促进协调的机构的一部分 绒毛膜促性腺激素受体α、β亚基在滋养细胞中的表达 差异化。关键词胎盘，基因转录， 螺旋-环-螺旋，绒毛膜促性腺激素，USF-1

OBJECTIVE: To determine whether the chorionic gonadotropin beta gene is regulated by E box-binding transcription factors. RESULTS Developmentally appropriate and cell-specific gene transcription is regulated in many organs by transcription factors binding to the E box motif. Examination of the human chorionic gonadotropin beta subunit 5'-flanking DNA revealed three E box-like motifs at -274 (A box), -135 (B box), and -126 (C box) relative to the start site of transcription. To examine whether these elements play a role in gene transcription, the A box, the B/C boxes or all three sites were mutated and activity was compared to wild-type activity. Transfection of JEG-3 choriocarcinoma cells demonstrated that individual E box mutations reduced basal transcription by approximately 50%, but fold-induction by cAMP (a hallmark of trophoblast function) was not dramatically changed. Mutation of all three E boxes led to a 75% reduction in basal transcription, but not the fold-induction by cAMP. Gel mobility-shift assays with the A box revealed two bands which were not specific for trophoblast cells, and supershift analysis with specific antisera to a variety of E box-binding proteins demonstrated that while none of the specific complexes contained the bHLH dimer partners E12/E47, at least one band contained the widely expressed transcription factor USF-1. FUTURE DIRECTIONS USF-1 has recently been demonstrated to bind an E box-like element in the common glycoprotein hormone alpha subunit promoter and contribute to transcriptional activation of this gene in mouse pituitary gonadotropin tumor cells. This suggests a role in placental CG expression as well, and we will examine whether USF-1 is part of a mechanism promoting coordinate expression of the CG alpha and beta subunits during trophoblast differentiation. KEY WORDS placenta, gene transcription, helix-loop-helix, chorionic gonadotropin, USF-1