Figure 2.

Sequential actions of DNA2 and FEN1 to remove a long RNA–DNA flap during Okazaki fragment maturation. RPA binds to long 5′ RNA-DNA flaps generated by Pol δ/PCNA and/or PIF1. The flap-bound RPA inhibits the action of FEN1 on the flaps and simultaneously recruits and stimulates DNA2 to cleave at the middle of the ssDNA strand, generating a shorter (∼8 nt) 5′ flap. FEN1 then dislodges DNA2 and cleaves at the junction between the ssDNA and dsDNA strands. DNA2 can also function alone to process long flaps. The RPA-mediated sequential actions of DNA2 and FEN1 or of DNA2 alone produce ligatable DNA nicks that can be joined to form intact lagging strand DNA.