Assuntos
DNA Bacteriano/genética , RNA Polimerases Dirigidas por DNA/genética , Escherichia coli/genética , Óperon , RNA Polimerase I/genética , Transcrição Gênica , Sítios de Ligação , DNA Bacteriano/metabolismo , DNA Viral/genética , DNA Viral/metabolismo , Escherichia coli/metabolismo , RNA Polimerase I/metabolismo , RNA Bacteriano/biossíntese , RNA Viral/biossíntese , Moldes GenéticosRESUMO
In vitro transcription of ribosomal RNA was studied on the DNA of the transducing bacteriphage lambdarifd 18, which carries an rRNA transcription unit from Escherichia coli. rRNA synthesis was preferential at all polymerase/DNA ratios tested, and at the optimal 0.3 weight ratio nearly 60% of the transcript was rRNA. At this ratio the principal product of transcription comigrated in acrylamide-agarose electrophoresis with authentic 30-S rRNA precursor synthesized in vivo. In the presence of rifampicin more than one equivalent of rRNA was synthesized, thus suggesting the existence of two initiation sites for rRNA on the phage DNA. Similar results were obtained on E. coli DNA. Preincubation with heparin virtually eliminated the transcription of rRNA, in sharp contrast with the results of similar experiments on bacterial DNA where rRNA genes were transcribed 4--5 times in the presence of heparin. The possible explanation of this difference between rRNA promotors on the phage and the bacterial DNA are discussed.
Assuntos
Colífagos/metabolismo , DNA Viral/metabolismo , RNA Ribossômico/biossíntese , Transcrição Gênica , DNA Bacteriano/metabolismo , RNA Polimerases Dirigidas por DNA/metabolismo , Escherichia coli/metabolismo , Heparina/farmacologia , RNA/biossíntese , Rifampina/farmacologia , Moldes GenéticosRESUMO
1. Ledakrin (C-283), a 1-nitro-9-aminopropylacridine derivative, inhibits RNA synthesis in vitro if the complex with DNA is formed in the presence of thiol. 2. Using several analogues of Ledakrin, it has been found that the 1-nitro group is essential for enhancement of the inhibition by thiol; the length of 9-aminoalkyl side chain also plays a role in the reaction between DNA and the dye. 3. It is suggested that the low inhibitory effect of Ledakrin in the absence of thiol compounds is due to a steric hindrance between neighbouring 1-nitro and 9-aminoalkyl groups. This hypothesis has been confirmed by assaying inhibition of RNA synthesis by several analogues of Ledakrin.