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Transcriptional pausing in a region important for plasmid NR1 replication control
X N Dong1, D D Womble, R H Rownd
1Department of Molecular Biology, Medical School, Northwestern University, Chicago, Illinois 60611.
Journal of Bacteriology
|December 1, 1987
Summary
RNA polymerase pauses during IncFII plasmid NR1 replication gene transcription. This pausing, enhanced by NusA protein, may regulate RepA1 protein synthesis and plasmid replication.
Area of Science:
- Molecular Biology
- Genetics
- Microbiology
Background:
- IncFII plasmid NR1 replication relies on the repA1 gene.
- RepA1 protein is essential for initiating NR1 plasmid replication.
- Regulation of RepA1 synthesis is crucial for controlling plasmid copy number.
Purpose of the Study:
- To investigate the transcriptional pausing in the leader region of the repA1 gene in IncFII plasmid NR1.
- To determine the role of NusA protein in this transcriptional pausing.
- To understand how transcriptional pausing affects the regulation of repA1 gene expression and plasmid replication.
Main Methods:
- In vitro single-round transcription assays.
- Northern blot RNA-DNA hybridization.
- Quantitative hybridization of pulse-labeled RNA.
Main Results:
- RNA polymerase pauses in the leader region preceding the repA1 gene of IncFII plasmid NR1.
- NusA protein enhances transcriptional pausing at these sites.
- In vivo studies confirm the presence of paused RNA intermediates, suggesting pausing does not cause premature termination.
- Pause sites are located between a countertranscript binding site and the repA1 coding sequence.
Conclusions:
- Transcriptional pausing in the repA1 leader region is a feature of IncFII plasmid NR1 replication control.
- Pausing, potentially regulated by NusA, may influence RepA1 protein synthesis and thus plasmid replication.
- This mechanism contributes to the overall regulation of plasmid NR1 copy number.