FAQ: What is cap 0 and cap 1?

Cap 0 is a N7-methyl guanosine connected to the 5′ nucleotide through a 5′ to 5′ triphosphate linkage, typically refers to as m7G cap or m7Gppp- in the literature. In the cell, the cap 0 structure is essential for efficient translation of the mRNA that carries the cap. An additional methylation on the 2′O position of the initiating nucleotide generates Cap 1, or refers to as m7GpppNm-, where Nm denotes any nucleotide with a 2′O methylation. Cap 1 has been shown to be important in evading the cellular innate immune response in vivo.