Global mapping of circRNA-target RNA interactions reveal P-body-mediated translational repression

Circular RNAs (circRNAs) are primarily produced through pre-mRNA back-splicing, yet their target repertoire and functional mechanisms remain elusive. Here, we present circTargetMap, a computational framework for globally mapping circRNA targets using RNA-RNA interactomes obtained via RNA in situ conformation sequencing (RIC-seq) in the hippocampus and ten human cell lines. This approach identified 117,163 high-confidence circRNA-target RNA interactions, with 83% of target mRNAs bound by multiple circRNAs. Functionally, CDR1as and circRMST repress target mRNA translation by sequestering them into processing bodies (P-bodies)-membraneless granules-through sequence-specific base-pairing, probably independent of AGO2, DICER, and microRNA (miRNAs). To directly capture granule-associated interactions, we developed the granule RIC-seq (GRIC-seq) method, revealing the broad role of circRNA-target RNA interactions in translational repression. Moreover, pathogenic variants are significantly enriched around circRNA-target RNA interaction sites, suggesting potential roles in disease. Our study provides valuable resources for circRNA functional exploration and a framework for investigating RNA-RNA interactions within membraneless organelles.