End group labelling of RNA and double stranded DNA by phosphate exchange catalyzed by bacteriophage T4 induced polynucleotide kinase.

End group labelling of sheared double-stranded DNA, and tRNA has been effected without prior dephosphorylation, utilizing the reversal of T₄ polynucleotide kinase activity. Incubation of DNA with polynucleotide kinase in the presence and absence of a phosphate acceptor (ADP) allowed the determination of the relative ratio of 5′ hydroxyl and 5′ phosphoryl terminii in the polynucleotide. This method of analysis has demonstrated a high preference in the formation of 5′ vs 3′ phosphomonoesters during high pressure shearing of double stranded DNA.