Relaxed Substrate Specificity in Qβ Replicase through Long-Term In Vitro Evolution

Kohtoh Yukawa,Norikazu Ichihashi,Ryo Mizuuchi

doi:10.3390/life12010032

Abstract

A change from RNA- to DNA-based genetic systems is hypothesized as a major transition in the evolution of early life forms. One of the possible requirements for this transition is a change in the substrate specificity of the replication enzyme. It is largely unknown how such changes would have occurred during early evolutionary history. In this study, we present evidence that an RNA replication enzyme that has evolved in the absence of deoxyribonucleotide triphosphates (dNTPs) relaxes its substrate specificity and incorporates labeled dNTPs. This result implies that ancient replication enzymes, which probably evolved in the absence of dNTPs, could have incorporated dNTPs to synthesize DNA soon after dNTPs became available. The transition from RNA to DNA, therefore, might have been easier than previously thought.

Highlights

IntroductionPhylogenetic analysis of polymerases between three domains of life support the notion that DNA polymerases (DNAPs) are derived from an ancestral RNA polymerase (RNAP) [10]
One of the major evolutionary events in primordial life would have been the change in the genetic material from RNA to DNA
We examined the incorporation of labeled riboand deoxyribonucleotides by the original and three mutant RNA polymerase (RNAP) that appeared during the course of the evolutionary experiment

Summary

Introduction

Phylogenetic analysis of polymerases between three domains of life support the notion that DNA polymerases (DNAPs) are derived from an ancestral RNA polymerase (RNAP) [10]. It is still largely unknown how such a transition could have occurred. RNAPs that had evolved and worked in such an environment might not have had strict substrate specificity and could have used dNTPs if available. The RNAPs with low substrate specificity could have immediately started the synthesis of DNA once dNTPs appeared and would have allowed for an easier transition from RNA to DNA as the genetic material. We hypothesized that RNAPs that evolved in the absence of dNTPs might be able to utilize dNTPs if they are available

Methods

Results

Conclusion