In some cases, the FEN1 lasts for only a short period of time and disengages from the replication complex. This causes a delay in the cleavage that the flaps displaced by Pol δ become long. When the RPA reaches a long enough length, it can bind stably. When the RPA bound flaps are refactorized to FEN1 cleavage the require another nuclease for processing, this has been identified as an alternate nuclease, DNA2. DNA2 has defects in the DEN1 overexpression. The DNA2 showed to work with FEN1 to process long flaps. DNA2 can dissociate the RPA from a long flap, it does this by using a mechanism like the FEN1. It binds the flap and threads the 5’ end of the flap. The nuclease cleaves the flap making it too short to bind to the RPA, the flap being too short means it is available for FEN1 and ligation. This is known as the long flap method. DNA2 can act as FEN1 as a backup for nuclease activity but it is not an efficient process.