During POLB-dependent long patch base excision repair (BER), PARP1 and/or PARP2 is recruited to the BER site along with flap endonuclease FEN1. PARP1 and/or PARP2 and FEN1 facilitate POLB-mediated strand displacement synthesis which involves incorporation of 2-10 nucleotides at the 3' end of the APEX1-created single strand break (SSB). After the DNA strand displacement synthesis is completed and the displaced strand is cleaved, POLB recruits DNA ligase I (LIG1) to ligate the SSB (Klungland and Lindahl 1997, Dimitriadis et al. 1998, Prasad et al. 2001, Lavrik et al. 2001, Tomkinson et al. 2001, Ranalli et al. 2002, Cistulli et al. 2004, Liu et al. 2005).