Repression by cyclic AMP receptor protein at a distance.

Area of Science:

• Molecular Biology
• Genetics
• Biochemistry

Background:

• Bacterial promoters often have multiple DNA binding sites for transcription factors.
• Repression of transcription typically occurs when factors bind near the start site, but upstream repression is less common.
• The cyclic AMP receptor protein (CRP) is a key regulator of Escherichia coli transcription, with multiple binding sites frequently observed.

Purpose of the Study:

• To investigate the interactions between upstream-bound CRP and RNA polymerase alpha subunits.
• To understand how these interactions influence promoter activity (enhancement or repression).
• To assess the prevalence of upstream repression by transcription factors.

Main Methods:

• Analysis of CRP-DNA interactions at specific promoters with tandem CRP binding sites.
• Examination of interactions between CRP and the C-terminal domains of RNA polymerase alpha subunits.
• Assessing the impact of disrupting CRP-alpha subunit interactions on promoter activity.

Main Results:

• Upstream-bound CRP interacts with RNA polymerase alpha subunit C-terminal domains regardless of its regulatory effect.
• Disruption of this interaction leads to altered promoter activity (either downregulation or upregulation).
• The location of the upstream CRP binding site dictates whether its interaction with the alpha subunit leads to repression or enhancement.

Conclusions:

• Upstream-bound CRP's interaction with RNA polymerase alpha subunits is crucial for both transcriptional enhancement and repression.
• The findings suggest that upstream repression by transcription factors may be more common than previously recognized.
• This has significant implications for annotating promoter functions in newly sequenced bacterial genomes.