DNA sequences shaped by selection for stability.
DNA sequences shaped by selection for stability.
复制标题
通过选择稳定性形成的DNA序列。
DOI：
10.1371/journal.pgen.0020022
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发表时间：
2006-02
期刊：
影响因子：
4.5
通讯作者：
Chao, Lin
中科院分区：
文献类型：
--
作者：
Ackermann, Martin;Chao, Lin
一段核苷酸的序列会影响其在复制和表达过程中出错的倾向。蛋白质是由稳定的还是不稳定的核苷酸序列编码的？如果对可变性的选择很普遍，人们可能会看到过多的不稳定序列。或者，如果针对错误的目标进行了大量的选择，则预计会有过多的稳定序列。我们筛选了不同生物的基因组序列，以寻找稳定性的一个重要决定因素，即单核苷酸重复的存在。我们发现，密码子用于编码蛋白质的方式避免了单核苷酸重复的出现，我们可以将这种偏向归因于选择而不是中性过程。这表明，对稳定性的选择，而不是对变异的产生，极大地影响了信息在基因组中的编码方式。突变是一把双刃剑。大多数突变都对生物体的健康有害。另一方面，如果没有突变，进化变化就不可能发生。突变的速度部分由有机体控制，而突变速度的一个决定因素是DNA序列本身。一些DNA序列在基因表达过程中容易发生突变和错误，而另一些序列则更稳定。生物通常在其基因中使用稳定或不稳定的DNA序列吗？这两种可能性似乎都有可能，而且这两种可能性都是假设的。为了回答这个问题，作者研究了生物体的DNA序列是否比预期的更稳定或更不稳定。他们分析了细菌、酵母和线虫的基因组，发现了压倒性的稳定DNA序列，这表明对遗传稳定性的选择比对变异世代的选择更重要。
The sequence of a stretch of nucleotides affects its propensity for errors during replication and expression. Are proteins encoded by stable or unstable nucleotide sequences? If selection for variability is prevalent, one could expect an excess of unstable sequences. Alternatively, if selection against targets for errors were substantial, an excess of stable sequences would be expected. We screened the genome sequences of different organisms for an important determinant of stability, the presence of mononucleotide repeats. We find that codons are used to encode proteins in a way that avoids the emergence of mononucleotide repeats, and we can attribute this bias to selection rather than a neutral process. This indicates that selection for stability, rather than for the generation of variation, substantially influences how information is encoded in the genome. Mutations are a double-edged sword. Most mutations are deleterious to an organism's fitness. On the other hand, without mutation, evolutionary change cannot occur. The rate of mutation is partially controlled by the organism, and one determinant of the mutation rate is the DNA sequence itself. Some DNA sequences are prone to mutations and errors during gene expression, whereas other sequences are more stable. Do organisms typically use stable or unstable DNA sequences in their genes? Both possibilities might seem plausible, and both have been postulated. To answer this question, the authors studied whether organisms' DNA sequences are more or less stable than expected by chance. Analyzing the genomes of a bacterium, a yeast, and a nematode, they find a overwhelming prevalence of stable DNA sequences, suggesting that selection for genetic stability is more important than selection for the generation of variation.
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