FAQ: What are Cap-0 and Cap-1?

Cap-0, commonly referred to as m7G cap or m7GpppN (where N signifies any ribonucleotide), is a N7-methyl guanosine connected by a 5′ to 5 triphosphate linkage to the 5 end of a transcript. Cap-dependent translation initiation, which is the primary mechanism of translation initiation in eukaryotes, requires cap 0 structure. 2′-O-methylation at the first position following the Cap-0 nucleotide generates Cap-1, which can also be represented by m7GpppNm-. Cap-1 has been shown to prevent inappropriate activation of antiviral innate immune receptors by endogenous transcripts in vivo.