Fig. 1.

The biological generating mechanisms of eccDNAs in vivo. A During the process of DNA replication and meiotic recombination, the excised DNA fragments can be circularized into eccDNAs through DNA damage repair mechanisms, including homologous recombination, NHEJ, MMEJ, mismatch repair, nucleotide excision repair and base excision repair. B Chromothripsis, episome model and BFB model were the major generating models of eccDNAs. C Apoptotic DNA fragments can be circularized into eccDNAs under the action of DNA ligase 3 after chromothripsis of apoptotic cells by DNase γ