A study finds that an RNA enzyme, or ribozyme, can evolve to produce complex RNAs efficiently but at the cost of synthesis accuracy. Key to the development of RNA-based life, which is thought to have preceded DNA-based life, is the ability to produce an RNA polymerase ribozyme, which can synthesize complex molecules and transmit genetic information to succeeding generations. Gerald Joyce, David Horning, and colleagues directed the evolution of an RNA polymerase ribozyme through 14 generations, selecting for the ability to synthesize functional ribozymes similar to itself. The evolution involved synthesis of a specific hammerhead ribozyme structure, and successful ribozymes were repeatedly tested in successively shortened synthesis durations to select for the most efficient and accurate ribozymes. The final generation exhibited the ability to synthesize its evolutionary ancestor, a class I ligase enzyme, in three separate RNA strands that then assembled into a functional ligase. Fidelity of synthesis was poor, however, given that few of the assembled ligases were free from function-disabling mutations. According to the authors, the results show the need for both efficient and accurate RNA synthesis in RNA-based life and suggest that accuracy of RNA synthesis may have been an obstacle along the evolutionary path of RNA-based life.
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Article #19-14282: "An RNA polymerase ribozyme that synthesizes its own ancestor," by Katrina F. Tjhung, Maxim N. Shokhirev, David P. Horning, and Gerald F. Joyce.
MEDIA CONTACT: Gerald F. Joyce, Salk Institute for Biological Studies, La Jolla, CA; tel: 858-732-9576?; e-mail: < gjoyce@salk.edu >
Proceedings of the National Academy of Sciences