Conformational changes of the upstream DNA mediated by H-NS and FIS regulate E. coli RrnB P1 promoter activity

Area of Science:

• Molecular Biology
• Genetics
• Biochemistry

Background:

• Ribosomal RNA (rRNA) transcription is crucial for cell growth and is regulated by proteins.
• FIS protein acts as an activator, while H-NS protein functions as a repressor of rRNA transcription.
• The precise antagonistic mechanisms of FIS and H-NS remain incompletely understood.

Purpose of the Study:

• To elucidate the cooperative mechanisms by which FIS and H-NS regulate rRNA transcription.
• To investigate how these two proteins achieve both positive and negative control over rRNA synthesis.

Main Methods:

• Electrophoretic mobility shift assays (EMSA) were employed to study protein-DNA interactions.
• DNA footprinting studies were conducted to map protein binding sites.
• DNA fragment circularization assays were used to assess DNA conformational changes.

Main Results:

• FIS and H-NS binding sites on promoter upstream DNA partially overlap.
• These proteins compete for binding, indicating an antagonistic interaction.
• Both proteins modulate DNA curvature, influencing DNA topology and transcription complex formation.

Conclusions:

• FIS and H-NS binding induces distinct DNA conformations, affecting transcription initiation.
• The interplay between FIS and H-NS provides a molecular basis for the dual regulation of stable RNA synthesis.
• These findings contribute to understanding the concerted action of transcription factors in gene regulation.