Differential regulation of telomerase activity by six telomerase subunits
Differential regulation of telomerase activity by six telomerase subunits
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DOI：
10.1046/j.1432-1033.2002.03025.x
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发表时间：
2002-07-01
期刊：
影响因子：
--
通讯作者：
Cheng, AJ
中科院分区：
文献类型：
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作者：
Chang, JTC;Chen, YL;Cheng, AJ
端粒酶是一种专门的逆转录酶，负责在染色体末端合成端粒DNA。已克隆了构成端粒酶复合物的六个亚基：hTR（人端粒酶RNA）、TEP1（端粒酶相关蛋白1）、hTERT（人端粒酶逆转录酶）、hsp90（热休克蛋白90）、p23和dyskerin。本研究探讨了端粒酶各亚单位对端粒酶活性的影响。通过下调或上调端粒酶，我们发现，只有hTERT的表达与端粒酶活性水平成正比。其他组分TEP1、hTR、hsp90、p23和dyskerin在整个调节过程中保持在高水平且不变。还进行了针对每个端粒酶组分的反义寡核苷酸的体内和体外实验。端粒酶活性被反义处理降低或消除。为了关联临床样本状态，检查了口腔癌患者的四对正常和恶性组织。除hTERT亚基在正常组织和癌组织中表达差异外，其他组分在正常组织和癌组织中均有表达。我们的结论是，hTERT是一个可调节的亚基，而其他组件在细胞中表达更恒定。虽然hTERT对酶活性具有限速作用，但其它端粒酶亚基（hTR、TEP1、hsp90、p23、dyskerin）参与了酶的全部活性。我们假设，一旦hTERT表达，所有其他端粒酶亚基可以组装，形成一个高度活跃的全酶。
Telomerase is a specialized reverse transcriptase responsible for synthesizing telomeric DNA at the ends of chromosomes. Six subunits composing the telomerase complex have been cloned: hTR (human telomerase RNA), TEP1 (telomerase-associated protein 1), hTERT (human telomerase reverse transcriptase), hsp90 (heat shock protein 90), p23, and dyskerin. In this study, we investigated the role of each the telomerase subunit on the activity of telomerase. Through down- or upregulation of telomerase, we found that only hTERT expression changed proportionally with the level of telomerase activity. The other components, TEP1, hTR, hsp90, p23, and dyskerin remained at high and unchanged levels throughout modulation. In vivo and in vitro experiments with antisense oligonucleotides against each telomerase component were also performed. Telomerase activity was decreased or abolished by antisense treatment. To correlate clinical sample status, four pairs of normal and malignant tissues from patients with oral cancer were examined. Except for the hTERT subunit, which showed differential expression in normal and cancer tissues, all other components were expressed in both normal and malignant tissues. We conclude that hTERT is a regulatable subunit, whereas the other components are expressed more constantly in cells. Although hTERT has a rate-limiting effect on enzyme activity, the other telomerase subunits (hTR, TEP1, hsp90, p23, dyskerin) participated in full enzyme activi`ty. We hypothesize that once hTERT is expressed, all other telomerase subunits can be assembled to form a highly active holoenzyme.