"NAD-capQ" detection and quantitation of NAD caps

RNA 5' cap structures comprising the metabolic effector nicotinamide adenine dinucleotide (NAD) have been identified in diverse organisms. Here we report a simple, two-step procedure to detect and quantitate NAD-capped RNA, termed "NAD-capQ." By use of NAD-capQ we quantitate NAD-capped RNA levels in Escherichia coli, Saccharomyces cerevisiae, and human cells, and we measure increases in NAD-capped RNA levels in cells from all three organisms harboring disruptions in their respective "deNADding" enzymes. We further show that NAD-capped RNA levels in human cells respond to changes in cellular NAD concentrations, indicating that NAD capping provides a mechanism for human cells to directly sense and respond to alterations in NAD metabolism. Our findings establish NAD-capQ as a versatile, rapid, and accessible methodology to detect and quantitate 5'-NAD caps on endogenous RNA in any organism.