EXO5 encodes a single-stranded DNA (ssDNA) bidirectional exonuclease that plays critical roles in DNA repair and genome stability 1. The protein contains an iron-sulfur cluster and exhibits both 5'-3' and 3'-5' exonuclease activities with strong preference for 5'-ends 1. EXO5 functions as a unique sliding exonuclease that loads at ssDNA ends and slides extensively along ssDNA before cutting, though this sliding activity is restricted by replication protein A (RPA) binding, which enforces 5'-directionality 1. The enzyme is involved in homology-directed recombination repair pathways and interstrand cross-link repair 23. EXO5 participates in ATR-dependent replication fork restart, where ATR phosphorylation regulates its nuclease activity and BLM helicase binding 4. Functionally deficient EXO5 leads to increased DNA damage sensitivity, chr1 abnormalities, and genomic instability 12. Germline mutations in EXO5, particularly the L151P variant, are associated with prostate cancer susceptibility through impaired DNA repair function 2. The gene is frequently epigenetically silenced across multiple cancer types, and elevated expression correlates with increased tumor mutation loads and poor patient survival 54.