Identification of Functionally Important Domains in the N-Terminal Region of Telomerase Reverse Transcriptase
Identification of Functionally Important Domains in the N-Terminal Region of Telomerase Reverse Transcriptase
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DOI：
10.1128/mcb.20.14.5196-5207.2000
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发表时间：
2000-07
影响因子：
5.3
通讯作者：
J. Xia;Yun Peng;I. Mian;N. Lue
中科院分区：
文献类型：
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作者：
J. Xia;Yun Peng;I. Mian;N. Lue
摘要端粒酶是一种核糖核蛋白逆转录酶，负责维持一条端粒末端重复序列。端粒酶复合体的关键蛋白亚基，称为TERT，具有逆转录酶样基序，可能介导催化作用。这些基序位于多肽的C-末端区域。基于隐马尔可夫模型的序列分析表明，在所有TERT的N-末端区域存在四个保守基序，分别为GQ、CP、QFP和T。保守残基的点突变分析证实了GQ基序的功能重要性。此外，Gq突变体的不同表型表明，该基序可能至少在端粒维持中发挥两种不同的功能。缺失分析表明，即使是酵母TERT最N端的非保守区(N区)也是端粒酶功能所必需的。该N区具有非特异性的核酸结合活性，可能反映了一个重要的生理功能。酵母TERT的不同部分在大肠杆菌中的表达研究表明，N区和GQ基序可能共同构成一个稳定的结构域。我们认为所有的TERT都可能有一个两部分的组织，N-GQ结构域通过一个灵活的连接子与其他基序相连。
ABSTRACT Telomerase is a ribonucleoprotein reverse transcriptase responsible for the maintenance of one strand of telomere terminal repeats. The key protein subunit of the telomerase complex, known as TERT, possesses reverse transcriptase-like motifs that presumably mediate catalysis. These motifs are located in the C-terminal region of the polypeptide. Hidden Markov model-based sequence analysis revealed in the N-terminal region of all TERTs the presence of four conserved motifs, named GQ, CP, QFP, and T. Point mutation analysis of conserved residues confirmed the functional importance of the GQ motif. In addition, the distinct phenotypes of the GQ mutants suggest that this motif may play at least two distinct functions in telomere maintenance. Deletion analysis indicates that even the most N-terminal nonconserved region of yeast TERT (N region) is required for telomerase function. This N region exhibits a nonspecific nucleic acid binding activity that probably reflects an important physiologic function. Expression studies of various portions of the yeast TERT inEscherichia coli suggest that the N region and the GQ motif together may constitute a stable domain. We propose that all TERTs may have a bipartite organization, with an N-GQ domain connected to the other motifs through a flexible linker.