TODAY’S edition of Nature (14 May 2009) features a landmark paper from researchers at the University of Manchester School of Chemistry that describes the synthesis of a pyrimidine ribonucleotide from simple chemicals, which may have existed on an early Earth. The research by Matthew Powner, in the laboratory of John Sutherland, represents a major stepping stone in support of the ‘RNA World’ theory, which describes the origins of life as passing through a stage in which RNA was the sole mediator of inheritance and catalysis, i.e. no DNA or proteins.
You can learn more about RNA World theory at the Exploring Origins website, or via resources on the website of Jack Szostak, one of the pre-eminent leaders in the field who also presents an accompanying perspective in this edition.
Whilst RNA is certainly a versatile molecule, with one form or another capable of breaking itself apart, joining itself to other RNA molecules, promoting formation of peptide linkages (the primary links of proteins) and templating its own self-replication, a major limiting point has existed regarding the origins of the necessary precursors for the RNA itself, i.e. ribonucleotides. Since the late 60’s, chemists studying prebiotic chemistry have focussed on trying to identify conditions in which these ribonucleotides would spontaneously assemble from their constituent parts: a nucleobase (which can be adenine, guanine, cytosine or uracil), a ribose sugar and phosphate. However, this approach was based on the assumption that these sub-units would assemble first, before combining to form the ribonucleotides. Unfortunately, no realistic conditions have been found in which a nucleobase would join to a ribose sugar.