Non-Enzymatic Assembly of a Minimized RNA Polymerase Ribozyme.

Falk Wachowius,Philipp Holliger

doi:10.1002/syst.201900004

Falk Wachowius, Philipp Holliger

Open Access

https://doi.org/10.1002/syst.201900004

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Abstract

Central to the “RNA world” hypothesis of the origin of life is the emergence of an RNA catalyst capable of RNA replication. However, possible replicase ribozymes are quite complex and were likely predated by simpler non-enzymatic replication reactions. The templated polymerisation of phosphorimidazolide (Imp) activated ribonucleotides currently appears as the most tractable route to both generate and replicate short RNA oligomer pools from which a replicase could emerge. Herein we demonstrate the rapid assembly of complex ribozymes from such Imp-activated RNA fragment pools. Specifically, we show assembly of a newly selected minimal RNA polymerase ribozyme variant (150 nt) by RNA templated ligation of 5’-2-methylimidazole-activated RNA oligomers <30 nucleotides long. Our results provide support for the possibility that complex RNA structures could have emerged from pools of activated RNA oligomers and outlines a path for the transition from non-enzymatic/chemical to enzymatic RNA replication.

Highlights

Central to the “RNA world” hypothesis of the origin of life is the emergence of an RNA catalyst capable of RNA replication
RNA polymerase ribozymes (RPR) generated by in vitro evolution[2] are credible candidates for a modern-day reconstruction of such a RNA replicase. How such large and complex ribozymes could have emerged from the pools of short RNA oligomers accessible from prebiotic chemistry (
We first defined optimal reaction conditions that would allow RNA polymerase ribozyme (RPR) activity to proceed in eutectic ice phases, where both de novo as well as templated non-enzymatic polymerisation of RNA could be demonstrated.[8b,11]

Summary

Introduction

Central to the “RNA world” hypothesis of the origin of life is the emergence of an RNA catalyst capable of RNA replication. After having minimized RPR size substantially and optimized activity, we investigated if the F ribozyme could be assembled from the short, activated RNA oligomers, such as would be accessible from untemplated non-enzymatic RNA polymerisation reactions.[14] Non-enzymatic polymerisation of RNA oligomers from 5’phosphorimidazole-activated monomers in ice generates preferentially short oligomers with maximum lengths of ~20 nt with a mixed base composition.[8b] On montmorillonite clay longer oligomers have been observed but only for low complexity sequences.[15] Optimized

Results

Conclusion