Telomere dynamics, end-to-end fusions and telomerase activation during the human fibroblast immortalization process
Telomere dynamics, end-to-end fusions and telomerase activation during the human fibroblast immortalization process
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DOI：
10.1038/sj.onc.1202797
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发表时间：
1999-07-22
期刊：
影响因子：
8
通讯作者：
Sabatier, L
中科院分区：
文献类型：
--
作者：
Ducray, C;Pommier, JP;Sabatier, L
细胞增殖过程中端粒重复序列的丢失可能在衰老中起作用，一般认为端粒酶的激活阻止了端粒的进一步缩短，并且对于细胞永生化是必不可少的。在这项研究中，我们通过定期监测末端限制性片段的大小分布，对四种SV 40转化的人成纤维细胞系进行了详细的细胞遗传学和分子特征分析，在整个永生化过程中端粒酶活性和相关的染色体不稳定性，在危机前细胞中，在培养物的寿命期间，平均TRF长度逐渐降低。在危机时，端粒达到临界尺寸，在细胞系中不同，有助于双着丝粒染色体的峰值，这主要是由于端粒缔合。我们观察到短端粒长度危机和染色体不稳定性之间的直接相关性。在两个永生细胞系中，虽然检测到端粒酶，但平均端粒长度仍继续减少，而相关的双着丝粒染色体的数量稳定。因此，端粒酶可以特异性地保护已经达到临界尺寸的端粒免受端到端双着丝粒的影响，而长端粒继续减少，尽管速度比危机前慢。这表明端粒酶的延长和端粒缩短之间的平衡，朝向稳定的“最佳”长度。
Loss of telomeric repeats during cell proliferation could play a role in senescence, It has been generally assumed that activation of telomerase prevents further telomere shortening and is essential for cell immortalization, In this study, we performed a detailed cytogenetic and molecular characterization of four SV40 transformed human fibroblastic cell lines by regularly monitoring the size distribution of terminal restriction fragments, telomerase activity and the associated chromosomal instability throughout immortalization, The mean TRF lengths progressively decreased in pre-crisis cells during the lifespan of the cultures, At crisis, telomeres reached a critical size, different among the cell lines, contributing to the peak of dicentric chromosomes, which resulted mostly from telomeric associations. We observed a direct correlation between short telomere length at crisis and chromosomal instability. In two immortal cell lines, although telomerase was detected, mean telomere length still continued to decrease whereas the number of dicentric chromosomes associated was stabilized. Thus telomerase could protect specifically telomeres which have reached a critical size against end-to-end dicentrics, while long telomeres continue to decrease, although at a slower rate as before crisis. This suggests a balance between elongation by telomerase and telomere shortening, towards a stabilized 'optimal' length.