Synthesis of hydrophobic-tagged 2′-deoxy-modified cap analogs and its effect on mRNA translation

Abstract

Messenger RNA (mRNA) has been implemented as COVID-19 vaccines. Following their success, the application of mRNA in cancer vaccines and protein replacement therapies is highly anticipated. The translational efficiency of mRNA largely depends on the cap structure located at its 5′ end. In particular, the Cap-1 and Cap-2 structures are known to exhibit higher protein synthesis levels than the Cap-0 structure. Previously, we developed a method called the PureCap technique, which utilizes reversed-phase high-performance liquid chromatography (RP-HPLC) to purify highly capped mRNA with high precision, enabling accurate evaluation of translational activity. In this study, we synthesized cap analogs incorporating deoxyribose, and evaluated their mRNA synthesis efficiency and translational activity. Furthermore, by optimizing the transcription reaction conditions using the synthesized DNA-modified Cap series, we successfully improved the capping efficiency and mRNA yield. The deoxyadenosine-modified cap analog synthesized using the PureCap technique demonstrated 3.2-fold higher translational activity than the standard Cap-1 structure. Additionally, when using tetranucleotide cap analogs, consistent translational activity was observed, regardless of base sequence differences. This confirmed the general applicability of DNA-modified mRNA for translational activity.