LIG1 and neoplasm: MMEJ machineries including DNA ligase III (LIG3), DNA ligase I (LIG1), and poly(ADP-ribose polymerase 1) (PARP1) are highly expressed in neural crest stem cells, the cell of origin for neuroblastoma, and thought to contribute to the tumor's ability to survive double-stranded break triggering events [41, 42].