Lee M S, Blackburn E H
Department of Microbiology and Immunology, University of California, San Francisco 94143-0414.
Mol Cell Biol. 1993 Oct;13(10):6586-99. doi: 10.1128/mcb.13.10.6586-6599.1993.
The ribonucleoprotein enzyme telomerase synthesizes one strand of telomeric DNA by copying a template sequence within the RNA moiety of the enzyme. Kinetic studies of this polymerization reaction were used to analyze the mechanism and properties of the telomerase from Tetrahymena thermophila. This enzyme synthesizes TTGGGG repeats, the telomeric DNA sequence of this species, by elongating a DNA primer whose 3' end base pairs with the template-forming domain of the RNA. The enzyme was found to act nonprocessively with short (10- to 12-nucleotide) primers but to become processive as TTGGGG repeats were added. Variation of the 5' sequences of short primers with a common 3' end identified sequence-specific effects which are distinct from those involving base pairing of the 3' end of the primer with the RNA template and which can markedly induce enzyme activity by increasing the catalytic rate of the telomerase polymerization reaction. These results identify an additional mechanistic basis for telomere and DNA end recognition by telomerase in vivo.
核糖核蛋白酶端粒酶通过复制酶RNA部分内的模板序列来合成端粒DNA的一条链。利用该聚合反应的动力学研究来分析嗜热四膜虫端粒酶的机制和特性。这种酶通过延长DNA引物来合成TTGGGG重复序列，即该物种的端粒DNA序列，该引物的3'端与RNA的模板形成结构域碱基配对。研究发现，该酶对短（10至12个核苷酸）引物的作用是非连续性的，但随着TTGGGG重复序列的添加会变得具有连续性。具有共同3'端的短引物5'序列的变化确定了序列特异性效应，这些效应不同于涉及引物3'端与RNA模板碱基配对的效应，并且可以通过提高端粒酶聚合反应的催化速率来显著诱导酶活性。这些结果确定了体内端粒酶识别端粒和DNA末端的另一个机制基础。
