T4 Polynucleotide Kinase can catalyze the transfer of the γ-phosphate group of ATP to the 5´-hydroxyl end and 3´-monophosphate nucleoside of the oligonucleotide chain (double-stranded or single-stranded DNA or RNA). T4 Polynucleotide Kinase also has 3´-phosphatase activity, which hydrolyzes 3´-phosphate groups from the 3´ phosphate ends of oligonucleotides, deoxy 3´-monophosphate nucleosides and deoxy 3´-diphosphate nucleosides .