TETRAHYMENA TELOMERASE CATALYZES NUCLEOLYTIC CLEAVAGE AND NONPROCESSIVE ELONGATION
TETRAHYMENA TELOMERASE CATALYZES NUCLEOLYTIC CLEAVAGE AND NONPROCESSIVE ELONGATION
复制标题
DOI：
10.1101/gad.7.7b.1364
复制
发表时间：
1993-07-01
影响因子：
10.5
通讯作者：
GREIDER, CW
中科院分区：
文献类型：
--
作者：
COLLINS, K;GREIDER, CW
端粒酶是一种核糖核蛋白酶，可将端粒重复序列添加到染色体上，从而维持端粒长度并稳定染色体末端。在体外，来自纤毛虫四膜虫的端粒酶通过添加四膜虫端粒序列 dT2G4 的重复序列来延长单链、富含鸟苷的 DNA 引物。除了前面描述的持续延伸反应之外，我们还鉴定了四膜虫端粒酶的两种活性：引物或产物 DNA 的 3'-5' 溶核切割和非持续延伸模式。溶核活性从引物 3' 末端去除了不符合端粒重复序列的残基，消除了 DNA 引物和 RNA 模板序列之间的不匹配。模板匹配的残基也从引物或产物 DNA 上切割下来。特定的引物长度、序列和浓度不同地刺激切割和进行性或非进行性延伸。这些新发现的活性表明端粒酶可能催化一系列端粒合成和修复功能，并表明端粒酶和 RNA 聚合酶之间的机制相似。根据我们的结果，我们提出了端粒酶引物结合、切割和延伸的模型。
Telomerase is a ribonucleoprotein enzyme that adds telomeric repeats to chromosomes, maintaining telomere length and stabilizing chromosome ends. In vitro, telomerase from the ciliate Tetrahymena elongates single-stranded, guanosine-rich DNA primers by adding repeats of the Tetrahymena telomeric sequence, dT2G4. We have identified two activities of Tetrahymena telomerase in addition to the previously described processive elongation reaction: a 3'-5' nucleolytic cleavage of primer or product DNA and a nonprocessive mode of elongation. The nucleolytic cleavage activity removed residues not conforming to the telomeric repeat sequence from a primer 3' end, eliminating mismatch between DNA primer and RNA template sequences. Template-matched residues were also cleaved from primer or product DNA. Specific primer lengths, sequences, and concentrations stimulated cleavage and processive or nonprocessive elongation differentially. These newly identified activities suggest that telomerase may catalyze a range of telomere synthesis and repair functions and suggest mechanistic similarities between telomerase and RNA polymerase enzymes. On the basis of our results, we propose a model for telomerase primer binding, cleavage, and elongation.