Chimeric archaeal BHB-human pre-tRNA scaffold HARBOR system enables versatile production of functional circular RNA modalities

Circular RNA (circRNA) molecules showcase enhanced stability and reduced immunogenicity compared to their linear counterparts, making them promising candidates for biomedical and biotechnological applications. Researchers have developed the HARBOR (Human-Archaeal RNA Backbone for Overexpression of Circular RNA) system, an innovative engineered platform that integrates a human precursor transfer RNA (pre-tRNA) scaffold with an archaeal Bulge-Helix-Bulge (BHB) motif.

This system leverages the existing tRNA splicing machinery within cells to create chimeric pre-tRNA intermediates, which, after processing, yield a wide range of circRNAs, from hundreds of nucleotides to 8 knt long, in both cell cultures and living organisms.

A key advantage of the HARBOR system is its ability to produce large-sized circRNAs with efficiency up to 80 times greater than the intronic complementary sequence-mediated back-splicing (3D5) system. Additionally, it facilitates protein expression from translatable circRNAs at a rate nearly 20 times higher than the Tornado system.

These remarkable characteristics make the HARBOR platform suitable for a wide array of applications, such as generating therapeutic aptamers to target neuroinflammation and pathological TDP-43 condensation, as well as creating protein-coding circRNAs encoding adenine base editors for genome editing and MYOD1 for transforming fibroblasts into myocytes.

In summary, the HARBOR system offers a versatile, scalable, and user-friendly approach to harnessing the potential of circRNAs for various engineering and biomedical purposes.