Transcription of rat liver chromatin by Escherichia coli RNA polymerase: template properties after protein restriction.

Transcription was determined in liver chromatin from rats fed for 6 days, an optimal (20%) or suboptimal (3%) amount of high-quality protein. Transcription by Escherichia coli RNA polymerase (EC 2.7.7.6) was lower after prolonged incubation with chromatin from rats fed 3% as compared with 20% protein. Differences were detected in the transcripts of the two types of chromatin after analysis by sucrose density gradient centrifugation. But no measurable differences were found in the melting profiles at low ionic strength of the two chromatin preparations. Transcription per milligram chromatin DNA was 25-fold higher using E. coli RNA polymerase instead of rat liver RNA polymerase II. The use of UTP as radioactive precursor in the absence of ATP, GTP and CTP resulted in a low labelling of RNA. One [lambda32P]UTP nucleotide was incorporated/8 UMP nucleotides. The product obtained was sensitive to ribonuclease treatment. In the presence of ATP, GTP and CTP [lambda-32P]UTP nucleotide incorporation was reduced and that of UMP nucleotide was increased giving a ratio of 1:188.