LIG1 (DNA ligase I), recruited to the long-patch base excision repair site through its interaction with POLB, ligates the 3' end of the single strand break (SSB), containing the newly synthesized multiple nucleotide repair patch, with the FEN1-processed 5' end of the SSB, thus completing the base excision repair (Prigent et al. 1994, Tomkinson et al. 2001, Ranalli et al. 2002, Balakrishnan et al. 2009).