RNA ligases.

T4 RNA ligase 1 catalyzes the ATP-dependent covalent joining of single-stranded 5'-phosphoryl termini of DNA or RNA to single-stranded 3'-hydroxyl termini of DNA or RNA. T4 RNA ligase 2 also catalyzes the joining of a 3'-hydroxyl terminus of RNA to a 5'-phosphorylated RNA or DNA; unlike T4 RNA ligase 1, this enzyme prefers double-stranded substrates. A truncated form of T4 RNA ligase 2 requires a pre-adenylated substrate for ligation. This unit describes specific reaction conditions, as well as applications such as radioactive labeling of the 3' termini of RNA, circularizing oligodeoxyribonucleotides and oligoribonucleotides, ligating oligomers and nicks, creating hybrid and chimeric DNA/RNA molecules, and miRNA cloning. (c) 2008 by John Wiley & Sons, Inc.