Viruses, characterized by their nucleocapsid which encloses genetic material (either DNA or RNA), rely on host cells for replication. Their evolutionary origins remain one of the fundamental questions in biology, given the potential role they might have played in early life by facilitating genetic exchanges between cellular lineages.

  To get deep insight into the origins of viruses, we proceeded engineering and directed evolution of non-viral protein capsules that encapsulate mRNA to mimic evolutionary process of primitive viruses. We used lumazine synthase derived from the thermophilic bacteria, Aquifex aeolicus as a model nonviral protein capsid. After the several rounds of directed evolution, artificial nucleocapsid variants showing various architectures were obtained. Cryo-electron microscopy and X-ray footprinting analysis indicate a structural evolution in both protein and RNA to enhance encapsulation efficacy. These lab-engineered particles provide a novel platform to study the evolution of primordial viruses and virus alternative biotechnology.

  Oparin published a book titled “The Origin of Life” in 1924, when modern science on origins of life started. One of the earliest prebiotic synthesis of biomolecules was reported by Miller in 1953, where amino acids were formed by spark discharges in strongly reducing gas mixtures. Since then, a large number of experiments on prebiotic syntheses have been conducted. It has been considered, however, that early Earth atmosphere was only weakly reducing since 1980s. If so, it became difficult to form amino acids by conventional energies. Recently it was proposed that amino acid precursors could be effectively formed even in weakly reducing atmospheres by solar energetic particles from the young Sun. In addition to endogenous production, extraterrestrial amino acids found in meteorites have been considered as an additional source for the first life on Earth. It was presumed that amino acids were formed by such equilibrium reactions as the Strecker synthesis on the early Earth and in extraterrestrial environments. Our laboratory experiments suggested that macromolecular amino acid precursors could be formed by particles irradiation. Such non-equilibrium chemical reactions should be considered for prebiotic chemistry.