Identification of NAD+ capped mRNAs in Saccharomyces cerevisiae

RNAs besides tRNA and rRNA contain chemical modifications, including the recently described 5' nicotinamide-adenine dinucleotide (NAD⁺) RNA in bacteria. Whether 5' NAD-RNA exists in eukaryotes remains unknown. We demonstrate that 5' NAD-RNA is found on subsets of nuclear and mitochondrial encoded mRNAs in Saccharomyces cerevisiae NAD-mRNA appears to be produced cotranscriptionally because NAD-RNA is also found on pre-mRNAs, and only on mitochondrial transcripts that are not 5' end processed. These results define an additional 5' RNA cap structure in eukaryotes and raise the possibility that this 5' NAD⁺ cap could modulate RNA stability and translation on specific subclasses of mRNAs.