Structure-specific nuclease with 5′-flap endonuclease and 5′-3′ exonuclease activities involved in DNA replication and repair. During DNA replication, cleaves the 5′-overhanging flap structure that is generated by displacement synthesis when DNA polymerase encounters the 5′-end of a downstream Okazaki fragment. It enters the flap from the 5′-end and then tracks to cleave the flap base, leaving a nick for ligation. Also involved in the long patch base excision repair (LP-BER) pathway, by cleaving within the apurinic/apyrimidinic (AP) site-terminated flap. Acts as a genome stabilization factor that prevents flaps from equilibrating into structures that lead to duplications and deletions. Also possesses 5′-3′ exonuclease activity on nicked or gapped double-stranded DNA, and exhibits RNase H activity. Also involved in replication and repair of rDNA and in repairing mitochondrial DNA.
