A certain lab mouse found this patent by Biontech in 2016. Amazing how they did all this work, 4 years before.

The "invention" also considers use of a promotor, possibly as used in Plasmid DNA.

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3' utr sequences for stabilization of rna

"...The term "nucleic acid sequence of the 3 ' -untranslated region of MT_R R1, a fragment thereof, or a variant of said nucleic acid sequence or fragment" relates to a nucleic acid sequence comprising, preferably consisting of a nucleic acid sequence selected from the group consisting of SEQ ID NOs : 105 to 121 of the sequence listing or a fragment thereof..."

patents.google.com/pate…