| In contrast with the rapidly expanding set of known biological roles for RNA, the known chemical diversity of cellular RNA has remained constant. The known chemical diversity of cellular RNA is limited primarily to canonical RNA, 3'-aminoacylated tRNAs, nucleobase-modified RNAs, and 5'-capped mRNAs in eukaryotes. This disparity between RNA's functional and chemical diversity, coupled with the powerful functional properties of synthetic small molecule-nucleic acid conjugates, led us to speculate that cellular small molecule-RNA conjugates beyond those previously described may exist. We have developed and applied high-resolution LC/MS screening methods to detect, in a broad manner, novel cellular small molecule-RNA conjugates. Application of these methods to E. coli and S. venezuelae total RNA revealed novel RNA-linked coenzyme A (CoA), RNA-linked nicotinamide adenine dinucleotide (NAD), in addition to a number of other putative small molecule-RNA conjugates not previously reported. The cofactors are novel examples of modification to cellular RNA that possess chemical functionality beyond the functional groups of canonical RNA. Subsequent experiments have begun to characterize these two cofactor conjugated cellular RNAs. The identification, characterization and efforts to fully elucidate the biological function of these modified RNAs will be described. These results provide new examples of small molecule-RNA conjugates and suggest that the chemical diversity of cellular RNA may be greater than previously understood. |
