Towards a Prebiotically Plausible Mechanism for the Emergence of RNA, Ribozymes and the RNA World

Available evidence, both in vitro and in vivo, attests to the descent of life from the RNA World; however, the prebiotic genesis of such RNA life remains ambiguous. How did The RNA World emerge from the abiotic chemistry on the Archean Earth? Montmorillonite clays have been shown to catalyze the polymerization of activated nucleotides (eg. adenosine 5′ phosphorimidazolide) into RNA, but polymerization has not previously been demonstrated for a prebiotically plausible nucleotide such as cyclic 2′, 3′-adenosine monophosphate (A>p). I reacted A>p in the presence of montmorillonite clay and could detect RNA polymers up to 5 nucleotides in length using a combination of HPLC, enzymatic labeling and mass spectrometry. This chemistry was found to be sensitive to pH and temperature. Reactions at pH 6 were found to produce more polymerization products than reactions at pH 7 or 8. Similarly A>p was found to be very stable at pH 6 with a hydrolysis rate at 25ºC of 6.2 x 10-9 sec-1 (t1/2 = 3.5 years) and at 4ºC of 4.4 x 10-10 sec-1 (t1/2 = 50 years). Also discussed are the requirements for the transition from abiotic chemistry to life. Important considerations for the emergence of replicating RNA networks from randomly synthesized RNA are outlined. Finally, the progress towards recreating the RNA world in the laboratory is summarized.