3' to 5' Translation of Circular RNAs?

Lin, Z.; Pi, X.; Lv, Z.; Liu, T.; Yin, H.; Shi, D.; Li, M.; Du, J.; Yang, Y.; Wang, S.; Wang, P.; Qin, Y.; Lin, W.; Tao, T.; Sun, L.; Chen, W.; Zhang, X.; Ji, Z.-L.

doi:10.64898/2025.12.08.692888

bioRxiv · 10.64898/2025.12.08.692888

3' to 5' Translation of Circular RNAs?

Lin, Z.·Pi, X.·Lv, Z.·Liu, T.·Yin, H.·Shi, D.·Li, M.·Du, J.·Yang, Y.·Wang, S.·Wang, P.·Qin, Y.·Lin, W.·Tao, T.·Sun, L.·Chen, W.·Zhang, X.·Ji, Z.-L.

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Abstract

For decades, the 5[->]3 direction of translation has been a central dogma of molecular biology(1). Here we present evidence that eukaryotic circular RNAs (circRNAs) can serve as templates for 3[->]5 backward translation (BT), yielding polypeptides with distinct sequence and structural features not found in canonical proteomes. Mining of more than 6,000 multi-omics datasets identified [~]1 million candidate BT proteins across eukaryotes, including 59,000 high-confidence human BT proteins supported by mass spectrometry. Genetic combinatorial experiments (KO and KI) and cell-free translation of synthetic circRNAs establish BT as a conserved mechanism. Loss-of-function studies of hs.circCAPN15 in human and dm.circROLS in Drosophila underscore the functional importance of BT-derived proteins. Our work challenges the long-standing unidirectional translation paradigm, expands the functional landscape of the genetic code, and reveals a hitherto hidden layer of proteomic complexity with broad implications for biology and therapeutics.

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Lin, Z., Pi, X., Lv, Z., Liu, T., Yin, H., Shi, D., Li, M., Du, J., Yang, Y., Wang, S., Wang, P., Qin, Y., Lin, W., Tao, T., Sun, L., Chen, W., Zhang, X., Ji, Z.-L.. 2025-12-09. 3' to 5' Translation of Circular RNAs?. https://doi.org/10.64898/2025.12.08.692888

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