A Retroviral Promoter and a Cellular Enhancer Define a Bipartite Element Which Controls env ERVWE1 Placental Expression
A Retroviral Promoter and a Cellular Enhancer Define a Bipartite Element Which Controls env ERVWE1 Placental Expression
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DOI：
10.1128/jvi.78.22.12157-12168.2004
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发表时间：
2004-11
影响因子：
5.4
通讯作者：
S. Prudhomme;G. Oriol;F. Mallet
中科院分区：
文献类型：
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作者：
S. Prudhomme;G. Oriol;F. Mallet
摘要 HERV-W 家族包含数百个在多种生理和病理背景下不同表达的基因座。一个名为 ERVWE1 的独特基因座编码参与类人猿胎盘生理学的包膜糖蛋白（合胞素）。在这里，我们表明，合胞素的表达受到二分元件的调节，该二分元件由与细胞增强子相邻的环AMP（cAMP）诱导的长末端重复（LTR）逆转录病毒启动子组成，赋予高水平的表达和胎盘向性。缺失突变体分析表明，ERVWE1 5' LTR 在位置 +1 至 +125 的区域中包含对于基础胎盘活性至关重要的结合位点。从位置+125到+310的区域代表在所有细胞类型中活跃的cAMP响应核心HERV-W启动子。定点诱变分析凸显了 U3 调控的复杂性。确定了 ERVWE1 胎盘特异性阳性（例如 T240）和阴性（例如 G71）调节位点，以及基本活动所需的重要位点（例如 A247）。 ERVWE1 原病毒的侧翼序列包含几个假定的调控元件。发现上游 HERV-H 和 HERV-P LTR 不活跃。相反，位于 HERV-P LTR 和 ERVWE1 之间的 436 bp 区域被证明是上游调节元件 (URE)，在胎盘细胞中具有显着活性。该 URE 充当组织特异性增强剂。对人科动物 URE 的遗传和功能分析揭示了人科动物和 Hylobatidae 成员的 URE 之间存在巨大差异。这些数据允许鉴定位置-436至-128的正调节区、位置-128至-67的哺乳动物表观LTR反转录转座子负调节区以及位置-67至-35的滋养层特异性增强子(TSE)。推定的 AP-2、Sp-1 和 GCMa 结合位点是 33 bp TSE 的重要组成部分。
ABSTRACT The HERV-W family contains hundreds of loci diversely expressed in several physiological and pathological contexts. A unique locus termed ERVWE1 encodes an envelope glycoprotein (syncytin) involved in hominoid placental physiology. Here we show that syncytin expression is regulated by a bipartite element consisting of a cyclic AMP (cAMP)-inducible long terminal repeat (LTR) retroviral promoter adjacent to a cellular enhancer conferring a high level of expression and placental tropism. Deletion mutant analysis showed that the ERVWE1 5′ LTR contains binding sites essential for basal placental activity in the region from positions +1 to +125. The region from positions +125 to +310 represents a cAMP-responsive core HERV-W promoter active in all cell types. Site-directed mutagenesis analysis highlighted the complexity of U3 regulation. ERVWE1 placenta-specific positive (e.g., T240) and negative (e.g., G71) regulatory sites were identified, as were essential sites required for basic activity (e.g., A247). The flanking sequences of the ERVWE1 provirus contain several putative regulatory elements. The upstream HERV-H and HERV-P LTRs were found to be inactive. Conversely, the 436-bp region located between the HERV-P LTR and ERVWE1 was shown to be an upstream regulatory element (URE) which is significantly active in placenta cells. This URE acts as a tissue-specific enhancer. Genetic and functional analyses of hominoid UREs revealed large differences between UREs of members of the Hominidae and the Hylobatidae. These data allowed the identification of a positive regulatory region from positions −436 to −128, a mammalian apparent LTR retrotransposon negative regulatory region from positions −128 to −67, and a trophoblast-specific enhancer (TSE) from positions −67 to −35. Putative AP-2, Sp-1, and GCMa binding sites are essential constituents of the 33-bp TSE.