National Natural Science Foundation of China (NSFC)
32222040
中国
National Natural Science Foundation of China (NSFC)
32070049
中国
Ministry of Science and Technology (MoST, China)
2021YFA1301900
中国
引用
ジャーナル: Nat Struct Mol Biol / 年: 2025 タイトル: Structural basis of circularly permuted group II intron self-splicing. 著者: Liu Wang / Jiahao Xie / Chong Zhang / Jian Zou / Zirui Huang / Sitong Shang / Xingyu Chen / Yang Yang / Jianquan Liu / Haohao Dong / Dingming Huang / Zhaoming Su / 要旨: Circularly permuted group II introns (CP introns) consist of rearranged structural domains separated by two tethered exons, generating branched introns and circular exons via back-splicing. ...Circularly permuted group II introns (CP introns) consist of rearranged structural domains separated by two tethered exons, generating branched introns and circular exons via back-splicing. Structural and mechanistic understanding of circular RNA (circRNA) generation by CP introns remains elusive. We resolve cryo-electron microscopy structures of a natural CP intron in different states during back-splicing at a resolution of 2.5-2.9 Å. Domain 6 (D6) undergoes a conformational change of 65° after branching, to facilitate 3'-exon recognition and circularization. Previously unseen tertiary interactions compact the catalytic triad and D6 for splicing without protein, whereas a metal ion, M, is observed to stabilize the 5'-exon during splicing. While these unique features were not observed in canonical group II introns and spliceosomes, they are common in CP introns, as demonstrated by the cryo-EM structure of another CP intron discovered by comparative genomics analysis. Our results elucidate the mechanism of CP intron back-splicing dynamics, with potential applications in circRNA research and therapeutics.