FIGURE 1.

Enzymatic reactions involved in RNA 5′ capping. RNA transcripts generated by in vitro transcription (usually done using T7 RNA polymerase or its variants; reaction 0) contains a triphosphate group at the 5′ end (pppR-). The 5′ triphosphate group can be converted to the Cap-1 structure (m⁷GpppRm-) through four enzymatic reactions carried out by RNA capping enzymes such as vaccinia RNA capping enzyme (reactions 1 through 3) in conjunction with vaccinia cap 2′-O-methyltransferase (reaction 4).