Evidence for the transcription os physiologically inactive rat-liver nucleolar chromatin by Escherichia coli RNA polymerase.
Rat-liver nucleoli (10-15 micrograms 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 of 3 units of Escherichia coli RNA polymerase. It was found that the nucleolar chromatin supporting the endogenous engaged RNA polymerase I transcription was completely 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 after 3 units of DNase I digestion. When hybridization experiments were conducted, it was found that the DNAs derived from both levels of DNase-I-digested 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.
D000818:Animals; D002466:Cell Nucleolus / Q000378:metabolism*; D002843:Chromatin / Q000378:metabolism*; D004247:DNA / Q000378:metabolism; D012321:DNA-Directed RNA Polymerases / Q000378:metabolism*; D003850:Deoxyribonuclease I; D003851:Deoxyribonucleases / Q000378:metabolism; D004720:Endonucleases / Q000378:metabolism; D004926:Escherichia coli / Q000201:enzymology*; D008099:Liver / Q000378:metabolism*; D008297:Male; D009693:Nucleic Acid Hybridization; D012313:RNA / Q000096:biosynthesis; D012318:RNA Polymerase I / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D013698:Templates, Genetic; D014158:Transcription, Genetic
D002843:Chromatin; D012313:RNA; D004247:DNA; D012321:DNA-Directed RNA Polymerases; D012318:RNA Polymerase I; D003851:Deoxyribonucleases; D004720:Endonucleases; D003850:Deoxyribonuclease I