5’-Hydroxyl Polyribonucleotide Kinase from HeLa Cell Nuclei

An enzyme, 5’-hydroxyl polyribonucleotide kinase, which catalyzes the phosphorylation of 5’-hydroxyl ends of RNA in the presence of ATP, has been isolated from extracts of HeLa cell nuclei. The kinase requires a divalent cation (Mg’+ or Mn’+) for activity, has an alkaline pH optimum, and is sensitive to the sulfhydryl antagonist N-ethylmaleimide. 5’-Hydroxyl terminated polydeoxyribonucleotides are phosphorylated much less efficiently than the 5’-hydroxyl terminated polyribonucleotides, and the kinase preparation is inactive on ribonucleoside 3’-monophosphates. Enzyme activity is inhibited by ADP and by pyrophosphate. The sedimentation coefficient of the kinase is estimated to be 5.6 S from glycerol gradient centrifugation.