A mutant telomerase defective in nuclear-cytoplasmic shuttling fails to immortalize cells and is associated with mitochondrial dysfunction
A mutant telomerase defective in nuclear-cytoplasmic shuttling fails to immortalize cells and is associated with mitochondrial dysfunction
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DOI：
10.1111/j.1474-9726.2010.00551.x
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发表时间：
2010-04-01
期刊：
影响因子：
7.8
通讯作者：
Santos, Janine H.
中科院分区：
文献类型：
--
作者：
Kovalenko, Olga A.;Caron, Matthieu J.;Santos, Janine H.
端粒酶是一种逆转录酶，专门参与端粒的合成。这种酶主要在细胞核中，它延长端粒，但许多报告表明，端粒酶的催化成分（在人类中称为hTERT）也位于细胞核外，包括线粒体中。已经报道了hTERT在细胞核和细胞质之间的穿梭，反之亦然，并且显示不同的蛋白质调节这种易位。端粒酶在亚细胞区室之间移动的确切原因仍然不清楚。在这项研究中，我们报告的突变，破坏了hTERT的核输出信号（内斯），使其核，但不能永生化细胞，尽管在体外保留的催化活性。原代成纤维细胞中突变蛋白的过表达与基于端粒的细胞衰老、多核细胞和DNA损伤反应基因ATM、Chk2和p53的激活相关。细胞中的线粒体功能也受到损害。我们发现，表达突变hTERT的细胞产生高水平的线粒体活性氧，并在端粒和端粒外DNA损伤。在ALT（端粒的替代性延长）细胞系中也观察到功能障碍的线粒体，该细胞系对由突变体hTERT诱导的生长停滞不敏感，表明线粒体损伤不是生长停滞的结果。我们的数据表明，涉及hTERT的内斯突变与端粒维持，线粒体功能和细胞生长的缺陷，并建议靶向该区域的hTERT作为一个潜在的新的癌症治疗策略。
Telomerase is a reverse transcriptase specialized in telomere synthesis. The enzyme is primarily nuclear where it elongates telomeres, but many reports show that the catalytic component of telomerase (in humans called hTERT) also localizes outside of the nucleus, including in mitochondria. Shuttling of hTERT between nucleus and cytoplasm and vice versa has been reported, and different proteins shown to regulate such translocation. Exactly why telomerase moves between subcellular compartments is still unclear. In this study we report that mutations that disrupt the nuclear export signal (NES) of hTERT render it nuclear but unable to immortalize cells despite retention of catalytic activity in vitro. Overexpression of the mutant protein in primary fibroblasts is associated with telomere-based cellular senescence, multinucleated cells and the activation of the DNA damage response genes ATM, Chk2 and p53. Mitochondria function is also impaired in the cells. We find that cells expressing the mutant hTERT produce high levels of mitochondrial reactive oxygen species and have damage in telomeric and extratelomeric DNA. Dysfunctional mitochondria are also observed in an ALT (alternative lengthening of telomeres) cell line that is insensitive to growth arrest induced by the mutant hTERT showing that mitochondrial impairment is not a consequence of the growth arrest. Our data indicate that mutations involving the NES of hTERT are associated with defects in telomere maintenance, mitochondrial function and cellular growth, and suggest targeting this region of hTERT as a potential new strategy for cancer treatment.