Ségal-Bendirdjian Evelyne, Geli Vincent
INSERM UMR-S 1124, Team: Cellular Homeostasis, Cancer and Therapies, INSERM US36, CNRS UMS 2009, BioMedTech Facilities, Université de Paris, Paris, France.
Marseille Cancer Research Center, U1068 INSERM, UMR 7258 CNRS, Aix Marseille University, Institut Paoli-Calmettes, Equipe labellisée Ligue, Marseille, France.
Front Cell Dev Biol. 2019 Dec 10;7:332. doi: 10.3389/fcell.2019.00332. eCollection 2019.
Telomerase plays a critical role in stem cell function and tissue regeneration that depends on its ability to elongate telomeres. For nearly two decades, it turned out that TERT regulates a broad spectrum of functions including signal transduction, gene expression regulation, and protection against oxidative damage that are independent of its telomere elongation activity. These conclusions that were mainly obtained in cell lines overexpressing telomerase were further strengthened by models of ectopic expression of telomerase or models of G1 knockout mice without detectable telomere dysfunction. However, the later models were questioned due to the presence of aberrantly shortened telomere in the germline of the parents that were used to create the G1 mice. The physiological relevance of the functions associated with overexpressed telomerase raised also some concerns due to artifactual situations and localizations and complications to quantify the level of TERT. Another concern with non-canonical functions of TERT was the difficulty to separate a direct TERT-related function from secondary effects. Despite these concerns, more and more evidence accumulates for non-canonical roles of telomerase that are non-obligatory extra-telomeric. Here, we review these non-canonical roles of the TERT subunit of telomerase. Also, we emphasize recent results that link TERT to mitochondria and protection to reactive oxygen species suggesting a protective role of TERT in neurons. Throughout this review, we dissect some controversies regarding the non-canonical functions of telomerase and provide some insights to explain these discrepancies. Finally, we discuss the importance of understanding these alternative functions of telomerase for the development of anticancer strategies.
端粒酶在干细胞功能和组织再生中发挥着关键作用,这取决于其延长端粒的能力。近二十年来,事实证明端粒酶逆转录酶(TERT)调节着广泛的功能,包括信号转导、基因表达调控以及抵抗氧化损伤,而这些功能与其端粒延长活性无关。这些主要在过表达端粒酶的细胞系中获得的结论,通过端粒酶异位表达模型或无可检测端粒功能障碍的G1敲除小鼠模型得到了进一步加强。然而,由于用于创建G1小鼠的亲代种系中存在异常缩短的端粒,后期模型受到了质疑。由于人为情况、定位以及量化TERT水平的复杂性,与过表达端粒酶相关的功能的生理相关性也引发了一些担忧。关于TERT非经典功能的另一个担忧是难以将直接的TERT相关功能与次要效应区分开来。尽管存在这些担忧,但越来越多的证据表明端粒酶具有非经典作用,这些作用是非必需的端粒外功能。在此,我们综述端粒酶TERT亚基的这些非经典作用。此外,我们强调了将TERT与线粒体以及对活性氧的保护联系起来的最新结果,这表明TERT在神经元中具有保护作用。在本综述中,我们剖析了关于端粒酶非经典功能的一些争议,并提供了一些见解来解释这些差异。最后,我们讨论了理解端粒酶这些替代功能对抗癌策略发展的重要性。