Coexistence of alternative lengthening of telomeres and telomerase in hTERT-transfected GM847 cells
Coexistence of alternative lengthening of telomeres and telomerase in hTERT-transfected GM847 cells
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DOI：
10.1128/mcb.21.12.3862-3875.2001
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发表时间：
2001-06-01
影响因子：
5.3
通讯作者：
Reddel, RR
中科院分区：
文献类型：
--
作者：
Perrem, K;Colgin, LM;Reddel, RR
先前已经证明，一些永生的人类细胞在端粒酶活性水平不高的情况下，通过一种被称为端粒选择性延长（ALT）的机制来维持其端粒。利用ALT的细胞的端粒长度非常不均匀，从很短到很长。本研究报告端粒酶表达对ALT细胞系GM847的影响。外源hTERT在GM847 （GM847/hTERT）细胞中的表达导致最短端粒延长；这是第一个证明ALT细胞中表达hTERT可以诱导端粒酶在端粒处活跃的证据。然而，在超过100倍的群体扩增后，GM847/hTERT细胞的端粒长度仍然出现快速波动。超长端粒和ALT相关的早幼粒细胞白血病（PML）体继续产生，表明外源性hTERT诱导的端粒酶活性并未消除ALT机制。相比之下，当GM847细胞系与两种不同的端粒酶阳性肿瘤细胞系融合时，每种情况下ALT表型都受到抑制。这些杂交细胞端粒酶呈阳性，端粒长度缩短，起初非常快，然后以端粒酶阴性的正常细胞的速度缩短。此外，alt相关的PML小体消失。端粒充分缩短后，端粒酶将其维持在一个稳定的长度。这些数据表明端粒酶阳性细胞含有一种抑制ALT机制的因子，但这种因子不太可能是端粒酶。此外，转染数据表明ALT和端粒酶可以在同一细胞中共存。
It has been shown previously that some immortalized human cells maintain their telomeres in the absence of significant levels of telomerase activity by a mechanism referred to as alternative lengthening of telomeres (ALT). Cells utilizing ALT have telomeres of very heterogeneous length, ranging from very short to very long. Here we report the effect of telomerase expression in the ALT cell line GM847. Expression of exogenous hTERT in GM847 (GM847/hTERT) cells resulted in lengthening of the shortest telomeres; this is the first evidence that expression of hTERT in ALT cells can induce telomerase that is active at the telomere. However, rapid fluctuation in telomere length still occurred in the GM847/hTERT cells after more than 100 population doublings. Very long telomeres and ALT-associated promyelocytic leukemia (PML) bodies continued to be generated, indicating that telomerase activity induced by exogenous hTERT did not abolish the ALT mechanism. In contrast, when the GM847 cell line was fused with two different telomerase-positive tumor cell lines, the ALT phenotype was repressed in each case. These hybrid cells were telomerase positive, and the telomeres decreased in length, very rapidly at first and then at the rate seen in telomerase-negative normal cells. Additionally, ALT-associated PML bodies disappeared. After the telomeres had shortened sufficiently, they were maintained at a stable length by telomerase. Together these data indicate that the telomerase-positive cells contain a factor that represses the ALT mechanism but that this factor is unlikely to be telomerase. Further, the transfection data indicate that ALT and telomerase can coexist in the same cells.