RNA phosphorylation: a polynucleotide kinase function in mouse L cell nuclei.

Analysis of [gamma-32P]ATP in vitro labeled nuclear RNA shows transfer of gamma-32P from ATP to form the 5'-terminal monophosphate for large RNA molecules. This finding is an actively transcribing nuclear system capable of guanylation and methylation reactions indicates that polynucleotide kinase activity in the eukaryotic nucleus may be functional in kinase reactions involving RNA. It further suggest a participation in the posttranscriptional modification reactions involved in RNA processing. All four nucleosides were found to act as acceptors at the 5' termini of RNA. It is also shown that both ATP and GTP can serve as donors in the nuclear polynucleotide kinase reaction.