5′-End Labeling of RNA with [γ-32P]ATP and T4 Polynucleotide Kinase

This protocol uses T4 polynucleotide kinase to catalyze the transfer of a radiolabeled, terminal (γ) phosphate of ATP to the 5′-hydroxyl terminus of a DNA or RNA molecule. The reaction is very efficient and hence is used as a general method for phosphorylating polynucleotides or oligonucleotides.