Characterization of an Ultra-Conserved Putative cis-Regulatory Module at the Mammalian Telomerase Reverse Transcriptase Gene
Characterization of an Ultra-Conserved Putative cis-Regulatory Module at the Mammalian Telomerase Reverse Transcriptase Gene
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DOI：
10.1089/dna.2009.0994
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发表时间：
2010-09-01
影响因子：
3.1
通讯作者：
Drewell, Robert A.
中科院分区：
文献类型：
--
作者：
Tran, Diana A.;Wong, Terence C.;Drewell, Robert A.
端粒是覆盖真核染色体末端的重复DNA序列的区域。它们作为一次性保护措施，防止由于DNA聚合酶无法将DNA复制到线性染色体末端而导致DNA复制过程中重要遗传信息的丢失。端粒酶催化以RNA分子为模板合成新的端粒重复序列。在胚胎干细胞中，编码端粒酶复合体催化蛋白亚单位(端粒逆转录酶[TERT])的基因在转录上是活跃的，对端粒延长至关重要，允许发育过程中持续的细胞分化。随着胚胎发育的进展，TERT基因被下调，以限制细胞的增殖能力。因此，在正常的成人体细胞中，TERT基因是沉默的。然而，在超过90%的癌症中，TERT基因被重新激活，使细胞绕过衰老而永生化。在这项研究中，我们探索了调控TERT基因转录表达的分子机制。对人类TERT基因周围非编码区的生物信息学分析发现，TERT超保守(TUC)模块位于转录起始点上游5kb。这一308个碱基的区域在远缘哺乳动物之间的保守率超过75%，在灵长类物种之间的保守率超过91%。在基于细胞的报告基因分析中测试了TUC区域的顺式调节潜力。瞬时转染HeLa和肺成纤维细胞表明TUC模块具有转录增强子活性。进一步的生物信息学分析表明，TUC区高度富含与造血相关蛋白的转录因子结合位点，表明TUC模块可能是特定细胞系中TERT基因的增强子。
Telomeres are regions of repeated DNA sequence that cap the ends of eukaryotic chromosomes. They act as disposable safeguards to prevent the loss of important genetic information during DNA replication due to the inability of DNA polymerase to replicate DNA to the ends of linear chromosomes. The synthesis of new telomeric repeats using an RNA molecule as a template is catalyzed by the enzyme telomerase. In embryonic stem cells, the gene encoding the catalytic protein subunit of the telomerase complex (telomere reverse transcriptase [TERT]) is transcriptionally active and critical for telomere elongation, allowing for continued cellular differentiation during development. The TERT gene is down-regulated as embryogenesis progresses to limit the proliferative capacity of cells. As a result, in normal human adult somatic cells the TERT gene is silenced. However, in over 90% of cancers, the TERT gene is reactivated, allowing cells to bypass senescence and become immortalized. In this study, we explore the molecular mechanisms that regulate transcriptional expression of the TERT gene. Bioinformatic analysis of the noncoding genomic regions around the human TERT gene identified a TERT ultra-conserved (TUC) module located 5 kb upstream of the transcription start site. This 308 bp region is over 75% conserved between distantly related mammalian species and over 91% conserved among primate species. The cis-regulatory potential of the TUC region was tested in cell-based reporter gene assays. Transient transfections into HeLa and lung fibroblast cells demonstrated that the TUC module has transcriptional enhancer activity. Further bioinformatic analysis revealed that the TUC region is highly enriched in putative transcription factor binding sites for proteins involved during hematopoiesis, indicating that the TUC module may be an enhancer for the TERT gene in specific cell lineages.