LIG3
DNA ligase 3 is an enzyme that, in humans, is encoded by the LIG3 gene. The human LIG3 gene encodes ATP-dependent DNA ligases that seal interruptions in the phosphodiester backbone of duplex DNA.
There are three families of ATP-dependent DNA ligases in eukaryotes. These enzymes utilize the same three step reaction mechanism; (i) formation of a covalent enzyme-adenylate intermediate; (ii) transfer of the adenylate group to the 5' phosphate terminus of a DNA nick; (iii) phosphodiester bond formation. Unlike LIG1 and LIG4 family members that are found in almost all eukaryotes, LIG3 family members are less widely distributed. The LIG3 gene encodes several distinct DNA ligase species by alternative translation initiation and alternative splicing mechanisms that are described below.