Faustovirus capping enzyme (FCE) catalyzed the addition of N7-methylguanosine cap (m7G) at the triphosphate and diphosphate positions at the 5′ end of the transcription product to produce RNA with Cap-0 cap. FCE is a monosubunit enzyme with three enzyme activities required to add Cap-0 cap structure to RNA: triphosphatase, guanine transferase, and (guanine-N7)-methyltransferase. The addition of Cap-0 cap structure, the first nucleotide 2′-O-methylation (Cap-1) and polyadenylation tailing (poly(A)) are key steps in eukaryotic mRNA maturation. The Cap-0 structure can also increase RNA stability and avoid triphosphorylated RNA activate the natural immune response.
FCE can maintain capping activity from low temperature to high temperature range of 55°C. Generally, 1 µl FCE (25 units) can be capped over 100 µg of RNA in 1 hour at 37°C. This product provides GTP and S-adenosylmethionine (SAM) required for capping activity.

UA070118: 25 U/μl Faustovirus Capping Enzyme in 40 mM Tris-HCl, 100 mM NaCl, 50 mM Arginine, 0.1 mM TCEP, 50% Glycerol (pH 8.0 @ 25°C)
10* Capping Buffer: 500 mM Tris-HCl, 50mM KCl, 10 mM MgCl2, 10mM DTT (pH 8 @ 25°C)

1. Combine RNA and Nuclease-free H2O to a final volume of 38 µl.
2. (Optional) Heat at 65°C for 5 minutes.
3. Place tube on ice.
4. Add the following components in the order specified:

5. Incubate at 37°C for 30 minutes.
6. RNA is now capped and ready for use in downstream applications. Some applications may require RNA to be purified prior to use.

1. Before incubating the mRNA solution with the Faustovirus Capping Enzyme, heat the mRNA solution at 65°C for 5 minutes to open the secondary structure at the 5' end of the transcription product. For highly structured 5' end transcription products, the time can be extended to 10 minutes or the denaturation temperature can be appropriately increased.

2. SAM is unstable at pH 7-8, 37°C and needs to be freshly configured before the reaction starts. To avoid SAM degradation, the working solution needs to be stored on ice.

3. RNase inhibitors can be added to the reaction system to prevent RNase contamination, and the recommended concentration is 1-2 U/μl.