Chemical and topological design of multicapped mRNA and capped circular RNA to augment translation

Protein and vaccine therapies based on mRNA would benefit from an increase in translation capacity. Here, we report a method to augment translation named ligation-enabled mRNA–oligonucleotide assembly (LEGO). We systematically screen different chemotopological motifs and find that a branched mRNA cap effectively initiates translation on linear or circular mRNAs without internal ribosome entry sites. Two types of chemical modification, locked nucleic acid (LNA) N⁷-methylguanosine modifications on the cap and LNA + 5 × 2′ O-methyl on the 5′ untranslated region, enhance RNA–eukaryotic translation initiation factor (eIF4E–eIF4G) binding and RNA stability against decapping in vitro. Through multidimensional chemotopological engineering of dual-capped mRNA and capped circular RNA, we enhanced mRNA protein production by up to tenfold in vivo, resulting in 17-fold and 3.7-fold higher antibody production after prime and boost doses in a severe acute respiratory syndrome coronavirus 2 vaccine setting, respectively. The LEGO platform opens possibilities to design unnatural RNA structures and topologies beyond canonical linear and circular RNAs for both basic research and therapeutic applications.