Generation of Long RNA Chains in Water

Giovanna Costanzo,Samanta Pino,Fabiana Ciciriello,Ernesto Di Mauro

doi:10.1074/jbc.m109.041905

Abstract

The synthesis of RNA chains from 3',5'-cAMP and 3',5'-cGMP was observed. The RNA chains formed in water, at moderate temperatures (40-90 degrees C), in the absence of enzymes or inorganic catalysts. As determined by RNase analyses, the bonds formed were canonical 3',5'-phosphodiester bonds. The polymerizations are based on two reactions not previously described: 1) oligomerization of 3', 5'-cGMP to approximately 25-nucleotide-long RNA molecules, and of 3',5'-cAMP to 4- to 8-nucleotide-long molecules. Oligonucleotide A molecules were further extended by reciprocal terminal ligation to yield RNA molecules up to >120 nucleotides long and 2) chain extension by terminal ligation of newly polymerized products of 3',5'-cGMP on preformed oligonucleotides. The enzyme- and template-independent synthesis of long oligomers in water from prebiotically affordable precursors approaches the concept of spontaneous generation of (pre)genetic information.

Highlights

We reasoned that for a pre-enzymatic polymerization to occur the solution must have relied on a simple and robust process
With sequences allowing good resolution, the average chain length (Navg) of the oligomers was determined by the equation number average (Navg) ϭ ⌺iniNi/⌺ini, where ni is the number of chain and Ni is the length of RNA chains in nucleotides
The afforded polymers were 5Ј-terminally labeled with [␥-32P]adenosine 5Ј-triphosphate (ATP) by T4 polynucleotide kinase, and the products were characterized by gel electrophoresis, allowing detailed evaluation of the lower sized oligomers

Summary

Introduction

We reasoned that for a pre-enzymatic polymerization to occur the solution must have relied on a simple and robust process. Coupled with the facile synthesis of all the nucleic bases from formamide [6] and with the formation of acyclonucleosides by TiO2-catalyzed formamide photochemistry [7], the nonenzymatic phosphorylation of nucleosides [5] shows that the formation of cyclic monophosphate nucleosides is chemically simple and prebiotically plausible. The formation of both 2Ј,3Ј- and 3Ј,5Ј-cyclic XMPs in water starting from nucleosides and an inorganic source was observed [8]. Nonenzymatic (pre)genetic polymerization could have taken place in warm little pond conditions, close to those imagined by Darwin [9]

Methods

Results

Conclusion