The RNA should have a 5´ cap (i.e., Cap-0 or Cap-1 RNA) and the first nucleotide adjacent to the cap must be adenine (+1 A). mRNA Cap N6 Methyltransferase (m6A) (NEB #M0767) will then methylate at the N6 position of the initiating adenine of the capped RNA.
Capped RNA can be prepared via in vitro transcription (NEB #E2040 or NEB #M2080) using cap analog or by enzymatic capping using Faustovirus Capping Enzyme (NEB #M2081) or Vaccinia Capping Enzyme (NEB #M2080), with or without mRNA Cap 2´-O-Methyltransferase (NEB #M0366).
