Advancing cap-independent mRNA translation

Messenger RNA (mRNA) technology, best known for its role in COVID-19 vaccines, also holds potential for treating cancer, as well as genetic and neurodegenerative diseases. These therapies depend on a molecular feature called the “cap” at the end of each mRNA strand, which protects the molecule and helps cells read it to make proteins. But in stressed cells – in diseases such as cancer or diabetes – the normal, cap-dependent protein production process can break down, limiting the effectiveness of mRNA-based treatments.

Some natural mRNAs can start protein production without the need for a cap, using internal sequences known as internal ribosome entry sites (IRESs) or cap-independent translation enhancers (CITEs). These “capless” mRNAs are, however, typically fragile, triggering strong unwanted immune responses and producing little protein. This makes them difficult to use therapeutically.

Now, researchers from Oxford Chemistry have published a new study in Nature Communications that introduces a chemical method to overcome these obstacles. Using a reagent called CleaN3, researchers added an azide “handle” to the end of capless mRNAs. This handle enables the controlled attachment of other molecules – through rapid and efficient coupling approach known as “click chemistry” – that improve the RNA’s stability, reduce the immune response, and increase protein production.

A video of this synthetic mRNA being delivered to cultured cells recently received an Honourable Mention in the 2025 Nikon Small World in Motion Competition.

Beyond improving performance, the team's technique makes it easier to study how cells translate mRNA without caps, using techniques such as flow cytometry and microscopy. It allows scientists to track mRNA inside cells, measure its levels, and map how it moves over time.

Overall, the new approach provides both a research tool and a potential path to more reliable, cap-independent mRNA therapeutics, expanding the reach of mRNA-based medicine beyond traditional capped designs.

Read more in Nature Communications.

Header image: A synthetic capless mRNA tracked inside a HeLa cell using 3D super-resolution microscopy.