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Repressor CopG prevents access of RNA polymerase to promoter and actively dissociates open complexes.

Hernández-Arriaga AM, Rubio-Lepe TS, Espinosa M, del Solar G - Nucleic Acids Res. (2009)

Bottom Line: First, CopG hindered binding of RNA polymerase to the promoter.Second, CopG was able to displace RNA polymerase once the enzyme has formed a stable complex with P(cr).A model for the CopG-mediated disassembly of the stable RNA polymerase-P(cr) promoter complex is presented.

View Article: PubMed Central - PubMed

Affiliation: Centro de Investigaciones Biológicas, Consejo Superior de Investigaciones Científicas, Madrid, Spain.

ABSTRACT
Replication of the promiscuous plasmid pMV158 requires expression of the initiator repB gene, which is controlled by the repressor CopG. Genes repB and copG are co-transcribed from promoter P(cr). We have studied the interactions between RNA polymerase, CopG and the promoter to elucidate the mechanism of repression by CopG. Complexes formed at 0 degrees C and at 37 degrees C between RNA polymerase and P(cr) differed from each other in stability and in the extent of the DNA contacted. The 37 degrees C complex was very stable (half-life of about 3 h), and shared features with typical open complexes generated at a variety of promoters. CopG protein repressed transcription from P(cr) at two different stages in the process leading to the initiation complex. First, CopG hindered binding of RNA polymerase to the promoter. Second, CopG was able to displace RNA polymerase once the enzyme has formed a stable complex with P(cr). A model for the CopG-mediated disassembly of the stable RNA polymerase-P(cr) promoter complex is presented.

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Summary of HO• footprints of the RNAP–Pcr complexes at 37°C. The schematized protection pattern corresponds to the footprinting experiment in Supplementary Figure S4. Promoter positions relative to the transcription start site are indicated. Protections are shown by brackets. Protections denoted by the same letter in both strands lie across the minor groove of the DNA. Enhancements are shown by arrows.
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Figure 7: Summary of HO• footprints of the RNAP–Pcr complexes at 37°C. The schematized protection pattern corresponds to the footprinting experiment in Supplementary Figure S4. Promoter positions relative to the transcription start site are indicated. Protections are shown by brackets. Protections denoted by the same letter in both strands lie across the minor groove of the DNA. Enhancements are shown by arrows.

Mentions: To analyze the mechanism by which CopG displaces RNAP from Pcr we determined the precise contacts of both proteins with the DNA backbone of the promoter/operator region (Figure 7 and Supplementary Figures S3 and S4).Figure 7.


Repressor CopG prevents access of RNA polymerase to promoter and actively dissociates open complexes.

Hernández-Arriaga AM, Rubio-Lepe TS, Espinosa M, del Solar G - Nucleic Acids Res. (2009)

Summary of HO• footprints of the RNAP–Pcr complexes at 37°C. The schematized protection pattern corresponds to the footprinting experiment in Supplementary Figure S4. Promoter positions relative to the transcription start site are indicated. Protections are shown by brackets. Protections denoted by the same letter in both strands lie across the minor groove of the DNA. Enhancements are shown by arrows.
© Copyright Policy - creative-commons
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2724298&req=5

Figure 7: Summary of HO• footprints of the RNAP–Pcr complexes at 37°C. The schematized protection pattern corresponds to the footprinting experiment in Supplementary Figure S4. Promoter positions relative to the transcription start site are indicated. Protections are shown by brackets. Protections denoted by the same letter in both strands lie across the minor groove of the DNA. Enhancements are shown by arrows.
Mentions: To analyze the mechanism by which CopG displaces RNAP from Pcr we determined the precise contacts of both proteins with the DNA backbone of the promoter/operator region (Figure 7 and Supplementary Figures S3 and S4).Figure 7.

Bottom Line: First, CopG hindered binding of RNA polymerase to the promoter.Second, CopG was able to displace RNA polymerase once the enzyme has formed a stable complex with P(cr).A model for the CopG-mediated disassembly of the stable RNA polymerase-P(cr) promoter complex is presented.

View Article: PubMed Central - PubMed

Affiliation: Centro de Investigaciones Biológicas, Consejo Superior de Investigaciones Científicas, Madrid, Spain.

ABSTRACT
Replication of the promiscuous plasmid pMV158 requires expression of the initiator repB gene, which is controlled by the repressor CopG. Genes repB and copG are co-transcribed from promoter P(cr). We have studied the interactions between RNA polymerase, CopG and the promoter to elucidate the mechanism of repression by CopG. Complexes formed at 0 degrees C and at 37 degrees C between RNA polymerase and P(cr) differed from each other in stability and in the extent of the DNA contacted. The 37 degrees C complex was very stable (half-life of about 3 h), and shared features with typical open complexes generated at a variety of promoters. CopG protein repressed transcription from P(cr) at two different stages in the process leading to the initiation complex. First, CopG hindered binding of RNA polymerase to the promoter. Second, CopG was able to displace RNA polymerase once the enzyme has formed a stable complex with P(cr). A model for the CopG-mediated disassembly of the stable RNA polymerase-P(cr) promoter complex is presented.

Show MeSH
Related in: MedlinePlus