FIGURE 3.

Strategies for enzymatic ligations. (A) T4 DNA ligase can help ligate double-stranded duplexes, such as DNA/RNA hybrids. With the help of cDNA bridge, T4 DNA ligase can achieve accurate RNA ligation. (B) T4 RNA ligase 1 catalyzes the nucleophilic attack of the 3′-OH terminus onto the activated 5′-terminus to form a covalent 5′, 3′-phosphodiester bond. The cDNA bridge can prevent the linear RNA precursor from folding into an unsuitable structure. (C) T4 RNA ligase 2 is suitable for linear RNA precursor with the ligation junction in a double-stranded region. With the help of RNA splint, T4 RNA ligase 2 can also realize the ligation of ends of ssRNA.