Rat-liver nucleoli (10–15 pg DNA) were digested with either 0.6 or 3 units of DNase I for various times (up to 1 h). RNA synthesis was then measured in the absence or presence ol 3 units of Escherichia coli RNA polymerase. It was found that the nucleolar chromatin supporting the endogenous engaged RNA polymerase I transcription was compl-etely destroyed in 3 min with either concentration of DNase I. The nucleolar chromatin template transcribed by E. coli RNA polymerase retained 50% of its original capacity even 60 min alter 3 units of DNase I digestion. When hybridization experiments were conducted, it was found that the DNAs derived from both levels of DNase-Idigested nucleoli were incapable of forming hybrids with the labelled nucleolar RNA synthesized by the engaged RNA polymerase I from the untreated nucleoli. Since the engaged RNA polymerase I transcribes only the physiologically active genes of the nucleolar chromatin, and the RNA transcripts represent active gene product, these data suggest that DNase I digestion has completely destroyed the active genes of the nucleolar chromatin, and E. coli RNA polymerase is able to transcribe the inactive nucleolar chromatin template.
Evidence for the transcription of physiologically inactive rat-liver nucleolar chromatin by Escherichia coli RNA polymerase
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Fu-Li Yu, Annabella Barrett; Evidence for the transcription of physiologically inactive rat-liver nucleolar chromatin by Escherichia coli RNA polymerase. Biosci Rep 1 March 1982; 2 (3): 155–161. doi: https://doi.org/10.1007/BF01116378
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