Joyce G F
Departments of Chemistry and Molecular Biology and the Skaggs Institute for Chemical Biology, The Scripps Research Institute, La Jolla, CA 92037, USA.
Cold Spring Harb Symp Quant Biol. 2009;74:17-23. doi: 10.1101/sqb.2009.74.004. Epub 2009 Aug 10.
A long-standing research goal has been to develop a self-sustained chemical system that is capable of undergoing Darwinian evolution. The notion of primitive RNA-based life suggests that this goal might be achieved by constructing an RNA enzyme that catalyzes the replication of RNA molecules, including the RNA enzyme itself. This reaction was demonstrated recently in a cross-catalytic system involving two RNA enzymes that catalyze each other's synthesis from a total of four component substrates. The cross-replicating RNA enzymes undergo self-sustained exponential amplification at a constant temperature in the absence of proteins or other biological materials. Amplification occurs with a doubling time of approximately 1 hour and can be continued indefinitely. Small populations of cross-replicating RNA enzymes can be made to compete for limited resources within a common environment. The molecules reproduce with high fidelity but occasionally give rise to recombinants that also can replicate. Over the course of many "generations" of selective amplification, novel variants arise and grow to dominate the population based on their relative fitness under the chosen reaction conditions. This is the first example, outside of biology, of evolutionary adaptation in a molecular genetic system.
一个长期的研究目标是开发一种能够进行达尔文式进化的自我维持化学系统。基于原始RNA的生命概念表明，这一目标或许可以通过构建一种能催化RNA分子复制（包括RNA酶自身）的RNA酶来实现。最近在一个交叉催化系统中证明了这种反应，该系统涉及两种RNA酶，它们能从总共四种组分底物催化彼此的合成。交叉复制的RNA酶在无蛋白质或其他生物材料的情况下，于恒定温度下进行自我维持的指数扩增。扩增以约1小时的倍增时间发生，并且可以无限期持续。少量交叉复制的RNA酶群体可在共同环境中竞争有限资源。这些分子以高保真度进行复制，但偶尔会产生也能复制的重组体。在许多“代”的选择性扩增过程中，新的变体出现并基于它们在所选反应条件下的相对适应性而增长，从而主导群体。这是分子遗传系统中生物学之外进化适应的首个例子。
