The human telomerase catalytic subunit hTERT: organization of the gene and characterization of the promoter
The human telomerase catalytic subunit hTERT: organization of the gene and characterization of the promoter
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DOI：
10.1093/hmg/8.1.137
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发表时间：
1999-01-01
影响因子：
3.5
通讯作者：
Bacchetti, S
中科院分区：
文献类型：
--
作者：
Cong, YS;Wen, JP;Bacchetti, S
端粒酶是一种合成端粒DNA的酶，在大多数人类体细胞中不表达，但在体外永生化和肿瘤发生过程中被激活，并被细胞分化抑制。在核心酶的两个组成部分中，催化蛋白hTERT的活性是有限的，为了研究hTERT基因的调控机制，我们克隆了包含完整hTERT转录单位的基因组序列。HTERT基因由16个外显子和15个内含子组成，跨度类似于35kb，瞬时转染带有潜在调控5‘序列的永生化细胞，结合对这些序列的缺失分析，表明负责启动子活性的元件包含在从ATG上游330个碱基延伸到基因第二外显子的区域内。不同细胞类型的分析表明，hTERT启动子在正常细胞和转化的永生化细胞中都是无效的，但与端粒酶一样，它在细胞永生化过程中被激活。序列分析表明，hTERT启动子富含GC，缺乏TATA和CAAT盒，但含有可能参与其调控的几种转录因子的结合位点。这些位点的丰富表明，hTERT的表达可能受到多种水平的控制，并在不同的细胞环境中受到不同因素的调节。
Telomerase, the enzyme that synthesizes telomeric DNA, is not expressed in most human somatic cells but is activated with in vitro immortalization and during tumorigenesis, and repressed by cell differentiation. Of the two components of the core enzyme, the catalytic protein hTERT is limiting for activity, To investigate mechanisms of hTERT gene regulation, we have cloned genomic sequences encompassing the complete hTERT transcription unit. The hTERT gene consists of 16 exons and 15 introns spanning similar to 35 kb, Transient transfections of immortal human cells with potential regulatory 5' sequences linked to a reporter, combined with deletion analysis of these sequences, indicated that elements responsible for promoter activity are contained within a region extending from 330 bp upstream of the ATG to the second exon of the gene. Assays in different cell types have shown that the hTERT promoter is inactive in normal and in transformed pre-immortal cells, but, like telomerase, it is activated with cell immortalization, Sequence analysis revealed that the hTERT promoter is GC-rich, lacks TATA and CAAT boxes but contains binding sites for several transcription factors that may be involved in its regulation. The abundance of these sites suggests the possibility that hTERT expression may be subject to multiple levels of control and be regulated by different factors in different cellular contexts.