TRANSCRIPTION OF REITERATED AND UNIQUE DNA SEQUENCES BY ENDOGENOUS RNA-POLYMERASES IN RAT-LIVER NUCLEOPLASM

A nucleoplasmic fraction isolated from rat liver nuclei was characterised with respect to in vitro transcription products by the use of mercurated CTP. At high salt concentrations which prevented initiation in vitro mercurated CTP was utilised as a substrate at about 50-60% of the efficiency of CTP. The difference was due to alteration of the elongation rates of the endogenous transcription complexes and not to selective inhibition of particular classes of enzymes. Hybridisation in vast DNA excess showed that more than 80% of the RNA could be driven into hybrid and that both reiterated and unique sequences were under transcription (mainly by RNA polymerase II) in the nucleoplasmic chromatin. © 1979.