T4 DNA Ligase is a ligation enzyme that can be used to join DNA fragments by catalyzing the formation of phosphodiester bonds betweenjuxtaposed 5" phosphate and 3" hydroxyl termini in double-stranded DNAusing ATP as a coenzyme. Both blunt and cohesive end DNA ligation, as well as single-stranded nick repair of DNA, RNA and DNA/RNA,are possible using the T4 DNA ligase.