Circular Photocaged mRNA for Light‐induced Late‐stage Activation of Translation

Abstract

ABSTRACT mRNA is a new medical modality as vaccine and raises hopes to become a protein replacement agent. Despite notable advances in manufacturing, stabilization and modification, its short half‐life remains a major limitation. Circular RNA bears potential to solve this issue, as degradation of mRNA proceeds primarily from the 5′ and 3′ ends. However, circular RNAs normally lack a 5′ cap and are less efficiently translated. We present a strategy to circularize mRNA covalently via click chemistry by modifying the 5′ cap and the 3′ poly(A) tail with bioorthogonal functional groups. The resulting Cyclic Click Cap‐containing mRNA (CyCliCap‐mRNA) is translationally muted by a photocleavable protecting group. Upon irradiation by light, the photocleavable protecting group is removed and the respective linear Cap0‐mRNA released. We show that CyCliCap‐mRNA can be activated for efficient translation at late timepoints (24‐48 h post transfection) in HeLa cells, which is not possible with the respective linear mRNA. The light‐mediated opening releases linear mRNA with a native Cap0 and thus overcomes the problem of inefficient translation of circular RNAs.