PT  - JOURNAL ARTICLE
AU  - Zonghao Qiu
AU  - Yang Zhao
AU  - Qiangbo Hou
AU  - Jiafeng Zhu
AU  - Mengting Zhai
AU  - Daolei Li
AU  - Yi Li
AU  - Chunxi Liu
AU  - Na Li
AU  - Yifei Cao
AU  - Jiali Yang
AU  - Zhenhua Sun
AU  - Chijian Zuo
TI  - Clean-PIE: a novel strategy for efficiently constructing precise circRNA with thoroughly minimized immunogenicity to direct potent and durable protein expression
AID  - 10.1101/2022.06.20.496777
DP  - 2022 Jan 01
TA  - bioRxiv
PG  - 2022.06.20.496777
4099  - http://biorxiv.org/content/early/2022/06/20/2022.06.20.496777.short
4100  - http://biorxiv.org/content/early/2022/06/20/2022.06.20.496777.full
AB  - Translatable circular RNAs (circRNAs) are emerging as a crucial molecular format for transient protein expression, with high potential to be an alternative for linear mRNA to reshape the landscape of mRNA pharmaceutical industry. Canonical Anabaena permuted intron-exon (Ana PIE) format that developed by ORNA is an efficient method for RNA circularization, and the engineered circRNAs direct supreme protein expression in eukaryotic cells. However, recent studies revealed that this method may unavoidably result in a remain of immunogenicity in the circRNA products, albeit after thorough RNA purification. In the current study, we develop a novel strategy for efficient generation of circRNA, via the permuted T4Td introns mediated autocatalytically ribozymatic reaction mediated ligation of the flanking segment sequences that concealing in ORF or translation initiation sequence (normally equal to IRES). This strategy universally realizes around 90% circularization effectivity, and the circRNA products can be purified to around 90% purity by our new purification method via HPLC, and presented thorough minimized immunogenicity, thus is termed “Clean-PIE”. The purified circRNAs are found to direct potent and durable expression of various proteins in vitro and in vivo. The partly purified Fluc circRNA by HPLC-SEC was found to direct Fluc expression in muscle for no less than 20 days. The highly purified circRNA exhibits much stronger protein expression in vitro and in vivo, and presumed a longer duration. Additionally, the scale-up of RNA circularization with the RNA precursors from 1 L transcription revealed high circularization effectivity (around 90%) and a high productivity of high-purity final circRNA products. Collectively, Clean PIE is a novel circRNA platform that possesses high circularization effectivity, enabled high RNA purity and thorough minimized immunogenicity, as well as scaling-up accessibility and directing extreme durability of protein expression, thus has the potential to develop advanced RNA vaccines and therapeutics in pharmaceutical industrial scale.Competing Interest StatementSome of the methods in this report are without details due to the potential business interest.