MRC Laboratory of Molecular Biology, Cambridge Biomedical Campus, Cambridge, United Kingdom.
Department of Physics, University of York, York, United Kingdom.
Elife. 2022 Feb 2;11:e75186. doi: 10.7554/eLife.75186.
RNA-catalyzed RNA replication is widely considered a key step in the emergence of life's first genetic system. However, RNA replication can be impeded by the extraordinary stability of duplex RNA products, which must be dissociated for re-initiation of the next replication cycle. Here, we have explored rolling circle synthesis (RCS) as a potential solution to this strand separation problem. We observe sustained RCS by a triplet polymerase ribozyme beyond full-length circle synthesis with strand displacement yielding concatemeric RNA products. Furthermore, we show RCS of a circular Hammerhead ribozyme capable of self-cleavage and re-circularization. Thus, all steps of a viroid-like RNA replication pathway can be catalyzed by RNA alone. Finally, we explore potential RCS mechanisms by molecular dynamics simulations, which indicate a progressive build-up of conformational strain upon RCS with destabilization of nascent strand 5'- and 3'-ends. Our results have implications for the emergence of RNA replication and for understanding the potential of RNA to support complex genetic processes.
RNA 催化的 RNA 复制被广泛认为是生命第一个遗传系统出现的关键步骤。然而，RNA 复制可能会受到双链 RNA 产物的非凡稳定性的阻碍，这些产物必须解离，才能重新开始下一个复制周期。在这里，我们探索了滚环合成 (RCS) 作为解决这个链分离问题的一种潜在方法。我们观察到三联体聚合酶核酶持续进行 RCS，其全长环合成伴随着链位移，产生串联 RNA 产物。此外，我们还展示了环形锤头核酶的 RCS，它能够自我切割和重新环化。因此，类病毒 RNA 复制途径的所有步骤都可以仅由 RNA 催化。最后，我们通过分子动力学模拟探索了潜在的 RCS 机制，结果表明 RCS 会逐渐积累构象应变，导致新生链 5'-和 3'-末端的不稳定。我们的研究结果对 RNA 复制的出现以及理解 RNA 支持复杂遗传过程的潜力具有重要意义。
