2022BBSRC-NSF/BIO: Self-replicating synthetic cells programmed by RNA

自从我们人类意识到生物和无生命物质之间存在明显的区别以来，我们一直在试图回答一个基本问题：是什么使生物有生命？这个问题有许多可能的答案，往往相互矛盾，但大多数对生命的定义都同意一点：生命应该能够自我复制。细胞复制确实是生命形式的一些最基本特征的基础，例如它们进化、生长、变形和适应环境的能力。注意到自我复制对生命的重要性之后，另一个问题自然出现了：是否有可能从头开始构建可以自我复制的东西，比如活细胞？当然，如果我们能做到，这将是从无生命物质中创造新生命的第一步，这将有助于我们理解最初导致地球上出现生命的原理，并具有巨大的技术潜力。感谢英国和美国科学家组成的国际团队，结合纳米技术，分子生物学，生物物理学和计算科学的专业知识，我们将解决这个基本问题，试图构建模拟生物细胞复制周期所有关键步骤的合成装置：1）遗传物质的复制，2）遗传物质在细胞的不同部分中的分离，3）细胞的生长和4）其在两个后代细胞中的分裂。多年来，许多研究人员已经，他致力于解决这个问题，并成功地建立了能够与这些单独步骤竞争的合成系统。然而，用同一个系统实现所有这些目标仍然很困难。一个关键的障碍是，合成系统将遗传物质的复制与包含它的外壳的生长和分裂结合起来是非常具有挑战性的，这样一个步骤就会触发另一个步骤。我们的方法通过重新思考核酸的作用来解决这个问题。在活细胞中，核酸主要是信息载体，DNA作为遗传信息的长期存储，RNA作为底物暂时保存这些信息，同时用于构建蛋白质。后者与其他一些大分子（它们本身由蛋白质机器合成）一起构成了细胞的主要结构元素。然而，在我们的自我复制合成细胞中，核酸（DNA和RNA）将扮演遗传和结构两种角色。我们的“合成细胞”将主要由DNA遗传密码产生的合成RNA纳米结构制成。RNA纳米结构将被设计成能够生长和分裂的细胞样装置，因为更多的RNA是从DNA中产生的，因此在遗传和结构复制之间建立了一种强有力的联系，这在以前的尝试中是缺失的。通过构建这些基于核酸的自我复制合成细胞，我们不仅能够衡量我们模仿生命形式的能力，并回答与生命起源有关的问题，但我们也将为改变游戏规则的技术应用铺平道路。从“自下而上”构建的合成细胞确实被认为在诊断和治疗方面具有潜在的非常有价值的价值，这些可编程设备可以在体内运行，识别疾病的存在，并通过局部产生和释放治疗有效载荷来有效地解决它。自我复制（以可控和安全的方式）的能力对于延长设备的寿命至关重要，因此其治疗作用的功效可以与基于重编程生物细胞的尖端疗法相媲美。

For as long as us humans have been aware that there is a clear difference between living and inanimate matter, we have been trying to answer a fundamental question: what makes something alive?This question has many possible answers, often at odds with each other, but most definitions of life agree on one point: Life should be able to self-replicate. Cell replication indeed underpins some of the most fundamental characteristics of life-forms, such as their ability to evolve, grow, morph, and adapt to their environment. Having noted how central self-replication is to life, another question naturally emerges: is it possible to build from scratch something that can replicate itself, like a living cell?Surely, if we could, it would be the first step towards creating new living things from inanimate matter, which would help us understand the principles that may have led to life emerging on planet earth in the first place, and hold dramatic technological potential.Thanks to an international team of UK and US scientists, combining expertise in nanotechnology, molecular biology, biophysics, and computational science, we will address this fundamental question, attempting to construct synthetic devices that mimic all critical steps of the replication cycle of biological cells: 1) replication of the genetic material, 2) segregation of the genetic material in different parts of the cell, 3) growth of the cell and 4) its division in two offspring cells.Many researchers have, over the years, worked on this problem, and succeeded in building synthetic systems capable of competing some of these individual steps. However, achieving all of them with the same system remains difficult. One key hurdle is that it is very challenging with synthetic systems to couple the replication of the genetic material with the growth and division of the enclosure that contains it, so that one step triggers the other.Our approach solves this problem by re-thinking the role of nucleic acids. In living cells, nucleic acids are predominantly information carriers, with DNA serving as the long-term storage of genetic information and RNA as a substrate to temporarily hold this information while it is used to build proteins. The latter, alongside few other macromolecules (themselves synthesised by protein-based machinery), constitute the main structural elements of the cell.In our self-replicating synthetic cells, however, nucleic acids (DNA and RNA) will play BOTH genetic AND structural roles. Our "synthetic cells" will be made primarily out of synthetic RNA nanostructures produced from a DNA genetic code. The RNA nanostructures will be designed to form cell-like devices capable of growing and dividing, as more RNA is produced from DNA, hence establishing a strong connection between genetic and structural replication, which was missing in previous attempts.By building these nucleic-acid-based, self-replicating synthetic cells, we will not only be able to gauge our ability to imitate life forms and answer questions relative to the origin of life, but we will also pave the way to game-changing technological applications. Synthetic cells constructed from the "bottom-up" are indeed regarded as potentially very valuable in diagnostics and therapeutics, whereby these programmable devices could operate in the body, recognise the presence of a disease, and efficiently tackle it by locally producing and releasing therapeutic payloads. The ability to self-replicate (in a controlled and safe manner) would be crucial for extending the lifespan of the devices, and thus the efficacy of their therapeutic action to the point that it could rival that of cutting-edge therapies based on reprogrammed biological cells.