Swiggers Susan J J, Nibbeling H Arno J, Zeilemaker Annelieke, Kuijpers Marianne A, Mattern Karin A, Zijlmans J Mark J M
Department of Hematology, Erasmus University Medical Center, Rotterdam, The Netherlands.
Exp Cell Res. 2004 Jul 15;297(2):434-43. doi: 10.1016/j.yexcr.2004.03.028.
The critical factors in the regulation of telomere length are not yet clearly defined. Telomerase is a key player in telomere elongation, although previous studies have shown that telomeres are differentially elongated after telomerase reconstitution. Moreover, a clear relation between the level of telomerase activity and telomere length was not observed. To investigate which factors are critical in telomere length regulation, we generated 24 telomerase-reconstituted primary human fibroblast clones. In these clones, in vitro telomerase activity level is clearly related to telomere length. High levels of telomerase activity are associated with longer telomeres and better telomere maintenance over time. The correlation coefficient, however, indicates that the level of telomerase activity is not the only factor in the regulation of telomere length. Clearly, factors that are not measured in an in vitro telomerase activity assay are involved in telomere length regulation in vivo. To investigate which telomerase components are critical in regulating telomerase activity levels, we studied expression levels of hTERT mRNA and hTR. Expression is highly variable between individual clones, but not related to the level of telomerase activity or telomere length. Our results indicate that expression levels of hTERT mRNA and hTR do not regulate the activity level of the telomerase complex, suggesting posttranscriptional modification of hTERT or the presence of additional proteins that modulate telomerase enzyme activity.
端粒长度调控中的关键因素尚未明确界定。端粒酶是端粒延长的关键因素，尽管先前的研究表明，端粒酶重建后端粒会有不同程度的延长。此外，并未观察到端粒酶活性水平与端粒长度之间存在明确的关系。为了研究哪些因素在端粒长度调控中至关重要，我们构建了24个端粒酶重建的原代人成纤维细胞克隆。在这些克隆中，体外端粒酶活性水平与端粒长度明显相关。高水平的端粒酶活性与更长的端粒以及随着时间推移更好的端粒维持相关。然而，相关系数表明端粒酶活性水平并非端粒长度调控中的唯一因素。显然，体外端粒酶活性测定中未检测到的因素参与了体内端粒长度的调控。为了研究哪些端粒酶成分在调节端粒酶活性水平中至关重要，我们研究了hTERT mRNA和hTR的表达水平。各克隆之间的表达差异很大，但与端粒酶活性水平或端粒长度无关。我们的结果表明，hTERT mRNA和hTR的表达水平不调节端粒酶复合物的活性水平，这表明hTERT存在转录后修饰或存在调节端粒酶活性的其他蛋白质。
