Co-transcriptional capping using an RNA capping enzyme-T7 RNA polymerase fusion protein

mRNA vaccines and therapeutics are highly effective and can be developed and manufactured with a relatively short lead time. Here we report an all-enzyme platform to generate capped synthetic RNA in a one-step process based on an RNA capping enzyme-T7 RNA polymerase fusion protein. Under standard in vitro transcription reaction conditions, the fusion protein, in conjunction with an RNA cap 2′-O-methyltransferase, can generate synthetic mRNA with up to 95% of Cap-1 incorporation, greatly simplifying mRNA manufacturing workflows. ### Competing Interest Statement S.H.C., D.K. and N.D. are current employees of New England Biolabs that markets molecular biology reagents. The affiliation does not affect the authors′ impartiality, adherence to journal standards and policies, or availability of data.