Non-enzymatic oligomerization of 3', 5' cyclic ribonucleotides

The very first origin of RNA is fraught with uncertainty. RNA world might have been preceded by an "unknown-polymer" world, or it might have started its polymerization destiny from highly activated precursors as phosphoramidated nucleotides. It might even have taken origin outside this planet. Each one of these scenarios has its appeals and drawbacks. Alternatively, RNA might have originated by self-polymerization of simple pre- biotically plausible compounds, i.e., 3',5' cyclic nucleotides. In this work, we review our observations about spontaneous polymerization of 3', 5' cyclic ribonucleotides and in particular of 3',5' cyclic cGMP. The reaction requires neither template, nor enzymatic activities, is thermodynamically favored, and selectively yields 3',5'-bonded oligoribonucleotides containing as many as 25 nucleotides.