Cascade of reduced speed and accuracy after errors in enzyme-free copying of nucleic acid sequences.
Cascade of reduced speed and accuracy after errors in enzyme-free copying of nucleic acid sequences.
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核酸序列的无酶复制出现错误后，速度和准确性会逐级降低。
DOI：
10.1021/ja3095558
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发表时间：
2013-01-09
影响因子：
15
通讯作者：
Chen, Irene A.
中科院分区：
文献类型：
--
作者：
Leu, Kevin;Kervio, Eric;Obermayer, Benedikt;Turk-MacLeod, Rebecca M.;Yuan, Caterina;Luevano, Jesus-Mario, Jr.;Chen, Eric;Gerland, Ulrich;Richert, Clemens;Chen, Irene A.
核酸的非酶促、模板指导的合成是自我复制系统的范例。这种系统的进化动力学取决于几个因素，包括突变率、相对复制率和突变序列的序列特征。我们测量了引物-模板错配（突变）下游正确和不正确单体插入的动力学，使用一系列骨架结构（RNA、DNA和LNA模板以及RNA和DNA引物）和两种类型的5′-活化核苷酸（氧氮苯并三唑和咪唑，即，核苷5 '-磷咪唑）。我们的研究表明，对于所研究的所有系统，初始不匹配很可能随后是另一个错误（54-75%的时间），并且在单个不匹配之后的扩展通常比没有错误的扩展慢10-100倍。如果错配之后是匹配的碱基对，则延伸速率恢复到接近正常水平。基于这些数据，我们模拟了计算机核酸复制，这表明由于后续错误的级联和动力学停滞，遭受初始错误的引物将落后于适当延伸的对应物，其中典型的突变事件由几个连续错误组成。我们的研究还包括不同的序列背景，这表明单体之间存在协同性，影响绝对速率（高达两个数量级）和保真度。这些结果表明，在无酶复制系统中的分子进化的特点是通过序列空间的大的“跳跃”，而不是孤立的点突变，也许能够快速探索不同的序列。这些发现也可能有助于设计结合高保真度和进化性的自我复制系统。
Non-enzymatic, template-directed synthesis of nucleic acids is a paradigm for self-replicating systems. The evolutionary dynamics of such systems depend on several factors, including the mutation rates, relative replication rates, and sequence characteristics of mutant sequences. We measured the kinetics of correct and incorrect monomer insertion downstream of a primer-template mismatch (mutation), using a range of backbone structures (RNA, DNA, and LNA templates and RNA and DNA primers) and two types of 5′-activated nucleotides (oxyazabenzotriazolides and imidazolides, i.e., nucleoside 5’-phosphorimidazolides). Our study indicated that for all systems studied, an initial mismatch was likely to be followed by another error (54-75% of the time) and extension after a single mismatch was generally 10-100 times slower than extension without errors. If the mismatch was followed by a matched base pair, the extension rate recovered to nearly normal levels. Based on these data, we simulated nucleic acid replication in silico, which indicated that a primer suffering an initial error would lag behind properly extended counterparts due to a cascade of subsequent errors and kinetic stalling, with the typical mutational event consisting of several consecutive errors. Our study also included different sequence contexts, which suggest the presence of cooperativity among monomers affecting both absolute rate (by up to two orders of magnitude) and fidelity. The results suggest that molecular evolution in enzyme-free replication systems would be characterized by large ‘leaps’ through sequence space rather than isolated point mutations, perhaps enabling rapid exploration of diverse sequences. The findings may also be useful for designing self-replicating systems combining high fidelity with evolvability.
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影响因子：
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作者：
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CRICK, FHC
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HOFACKER, IL;FONTANA, W;SCHUSTER, P
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