T4 RNA Ligase 1 (ssRNA Ligase)

T4 RNA ligase 1 is an enzyme that can catalyze the formation of phosphodiester bonds between 5'-phosphate (5'-P) termini and 3'-hydroxyl (3'-OH) termini either within or between single-stranded RNA (ssRNA), single-stranded DNA (ssDNA), or mononucleotides, and its activity depends on ATP. T4 RNA ligase 1 exhibits the highest ligation efficiency between RNA molecules, lower efficiency between DNA and RNA, and the lowest efficiency between DNA molecules, and is therefore also regarded as a single-stranded RNA ligase.

When T4 RNA ligase 1 is used for ligation between RNA molecules, the presence of a 5'-phosphate group and a 3'-hydroxyl group is required. When it is used for ligation between RNA and mononucleotides, the mononucleotide must be phosphorylated at both the 5' and 3' termini. For ligation between DNA and RNA, higher efficiency is obtained when DNA provides the 5'-phosphate group and RNA provides the 3'-hydroxyl group, whereas ligation efficiency is very low when DNA provides the 3'-hydroxyl group and RNA provides the 5'-phosphate group. When used for ligation between DNA molecules, the efficiency is extremely low. T4 RNA ligase 1 is commonly used for RNA circularization, 3'-end labeling of RNA, and the synthesis of oligo RNA and oligo DNA.