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Effects of antibiotics on RNA polymerase III transcription
1Biology Department, University of Massachusetts, Boston 02125.
Abstract:
We investigated the effects of six drugs on an RNA polymerase III in vitro transcription system. Adriamycin, daunorubicin, heparin, rifamycin AF/013, streptolydigin, and streptovaricin all inhibit RNA synthesis from a tRNA gene or the adenovirus 2 (AD2) VA1 RNA gene. The completed RNA polymerase III transcription complex is formed by the sequential, ordered addition of protein factors. Although both genes reportedly use the same transcription fractions for in vitro RNA synthesis, some of these drugs interfere differentially with these genes. A drug concentration that inhibits transcription from one gene may not inhibit transcription from the other gene. Adriamycin seems to block transcription if added between the binding of the individual transcription fractions. Daunorubicin appears to inhibit VA transcription only if added prior to both transcription fractions, but inhibits tRNA synthesis before and during transcription factor binding. Heparin blocks both genes between factors binding to DNA and after factor binding. Rifamycin blocks VA synthesis more effectively than tRNA synthesis. Streptolydigin blocks transcription of both genes. Streptovaricin probably blocks transcription by inhibiting early transcription complex assembly events. These drugs appear useful as appropriate probes to investigate transcription complexes since several discriminate between complexes formed on different genes during the assembly process.
Insights
Six drugs were tested for their effects on RNA polymerase III transcription. Some drugs differentially inhibit transcription of tRNA and adenovirus 2 VA1 RNA genes, acting as probes for transcription complex assembly.
Area of Science:
- Molecular Biology
- Biochemistry
- Genetics
Background:
- RNA polymerase III (Pol III) transcribes essential non-coding RNAs, including transfer RNA (tRNA) and adenovirus 2 (AD2) VA1 RNA.
- Pol III transcription involves a sequential assembly of protein factors on DNA.
- Understanding the assembly process is crucial for deciphering gene regulation and developing targeted therapies.
Purpose of the Study:
- To investigate the inhibitory effects of six specific drugs on the RNA polymerase III in vitro transcription system.
- To determine if these drugs exhibit differential inhibition patterns between tRNA and AD2 VA1 RNA gene transcription.
- To evaluate the potential of these drugs as molecular probes for studying transcription complex assembly.
Main Methods:
- An in vitro transcription system utilizing RNA polymerase III was employed.
- Six drugs (Adriamycin, daunorubicin, heparin, rifamycin AF/013, streptolydigin, and streptovaricin) were added at various stages of the transcription complex formation.
- The synthesis of RNA from both a tRNA gene and the AD2 VA1 RNA gene was measured to assess drug effects.
Main Results:
- All six tested drugs inhibited RNA synthesis from at least one of the genes.
- Differential inhibition was observed; a drug concentration inhibiting one gene's transcription did not necessarily inhibit the other.
- Specific drugs like Adriamycin, daunorubicin, and heparin showed distinct inhibitory effects depending on the timing of their addition during transcription factor binding and assembly.
Conclusions:
- The tested drugs exhibit differential effects on RNA polymerase III transcription of different genes.
- These drugs can act as valuable probes to dissect the ordered assembly of transcription complexes.
- Understanding drug-specific inhibition mechanisms provides insights into the dynamic nature of transcription initiation and factor interactions.