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Cloning of the complete gene for carcinoembryonic antigen: analysis of its promoter indicates a region conveying cell type-specific expression.

机译:癌胚抗原完整基因的克隆:对其启动子的分析表明,该区域表达了细胞类型特异性表达。

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Carcinoembryonic antigen (CEA) is a widely used tumor marker, especially in the surveillance of colonic cancer patients. Although CEA is also present in some normal tissues, it is apparently expressed at higher levels in tumorous tissues than in corresponding normal tissues. As a first step toward analyzing the regulation of expression of CEA at the transcriptional level, we have isolated and characterized a cosmid clone (cosCEA1), which contains the entire coding region of the CEA gene. A close correlation exists between the exon and deduced immunoglobulin-like domain borders. We have determined a cluster of transcriptional starts for CEA and the closely related nonspecific cross-reacting antigen (NCA) gene and have sequenced their putative promoters. Regions of sequence homology are found as far as approximately 500 nucleotides upstream from the translational starts of these genes, but farther upstream they diverge completely. In both cases we were unable to find classic TATA or CAAT boxes at their expected positions. To characterize the CEA and NCA promoters, we carried out transient transfection assays with promoter-indicator gene constructs in the CEA-producing adenocarcinoma cell line SW403, as well as in nonproducing HeLa cells. A CEA gene promoter construct, containing approximately 400 nucleotides upstream from the translational start, showed nine times higher activity in the SW403 than in the HeLa cell line. This indicates that cis-acting sequences which convey cell type-specific expression of the CEA gene are contained within this region.
机译:癌胚抗原(CEA)是一种广泛使用的肿瘤标志物,尤其是在结肠癌患者的监测中。尽管CEA也存在于一些正常组织中,但显然在癌组织中其表达水平高于相应的正常组织中。作为在转录水平上分析CEA表达调控的第一步,我们已经分离并鉴定了粘粒克隆(cosCEA1),该克隆包含CEA基因的整个编码区。外显子与推定的免疫球蛋白样结构域边界之间存在密切的相关性。我们已经确定了CEA和与其密切相关的非特异性交叉反应抗原(NCA)基因的转录起始簇,并对它们的推定启动子进行了测序。在这些基因的翻译起始位点上游约500个核苷酸处发现了序列同源性区域,但在更远的上游它们却完全分开。在这两种情况下,我们都无法在其预期位置找到经典的TATA或CAAT盒子。为了表征CEA和NCA启动子,我们在生产CEA的腺癌细胞系SW403和未生产的HeLa细胞中用启动子指示基因构建物进行了瞬时转染测定。一个CEA基因启动子构建体,在翻译起点上游包含约400个核苷酸,在SW403中显示的活性是在HeLa细胞系中的9倍。这表明在该区域内包含表达CEA基因的细胞类型特异性表达的顺式作用序列。

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