Enzyme-free genetic copying of DNA and RNA sequences.

Marilyne Sosson,Clemens Richert

doi:10.3762/bjoc.14.47

Abstract

The copying of short DNA or RNA sequences in the absence of enzymes is a fascinating reaction that has been studied in the context of prebiotic chemistry. It involves the incorporation of nucleotides at the terminus of a primer and is directed by base pairing. The reaction occurs in aqueous medium and leads to phosphodiester formation after attack of a nucleophilic group of the primer. Two aspects of this reaction will be discussed in this review. One is the activation of the phosphate that drives what is otherwise an endergonic reaction. The other is the improved mechanistic understanding of enzyme-free primer extension that has led to a quantitative kinetic model predicting the yield of the reaction over the time course of an assay. For a successful modeling of the reaction, the strength of the template effect, the inhibitory effect of spent monomers, and the rate constants of the chemical steps have to be determined experimentally. While challenges remain for the high fidelity copying of long stretches of DNA or RNA, the available data suggest that enzyme-free primer extension is a more powerful reaction than previously thought.

Highlights

Replication of genetic information is critical for all living systems
A solution to the chicken/egg dilemma of replication might be found in RNA, as oligo- and polyribonucleotides can encode genetic information and can catalyze biochemical reactions as ribozymes
Unlike assays performed with pre-activated monomers, primer extension with in situ activation of ribonucleotides led to significant levels of oligomers that form via untemplated polymerization of the nucleotides [63]

Summary

Introduction

Replication of genetic information is critical for all living systems. In the cell, this process is catalyzed by enzymatic machineries that have polymerases at their core [1]. One factor that significantly affects whether an enzyme-free primer extension reaction occurs in high yield or not is the strength of the template effect. The data mentioned above suggest that there is a strong dependence of the templating base and sequence context on the rate of enzyme-free primer extension assays.

Results

Conclusion