DNA ligases together with RNA ligases and mRNA capping enzymes constitute the nucleotidyl transferase superfamily. DNA ligases play a vital role in the diverse processes of DNA replication, recombination and repair, catalyzing the joining of interruptions in the phosphodiester backbone of duplex DNA, thereby utilizing either ATP or NAD+ as nucleotide cofactor. Multiple DNA ligases exist, yet all the eukaryotic ATP-dependent DNA ligases are related in sequence and structure, sharing a common catalytic region comprising a DNA-binding domain, a nucleotidyltransferase (NTase) domain, and an oligonucleotide/oligosaccharide binding (OB)-fold domain. Deficiency in either DNA ligase I, DNA ligase III, or DNA ligase IV causes different phenotypes of mammalian cell lines.
 T Ellenberger et al. EukaryoticDNA ligases: structural and functional insights. Annu Rev Biochem. 2008;77:313-38.
 IV Martin et al. ATP-dependentDNA ligases. Genome Biol. 2002;3(4):REVIEWS3005. Epub 2002 Mar 19.