Transcriptional activator C protein-mediated unwinding of DNA as a possible mechanism for mom gene activation

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Repressing Gene Transcription by Redirecting Cellular Machinery with Chemical Epigenetic Modifiers
10:28

Repressing Gene Transcription by Redirecting Cellular Machinery with Chemical Epigenetic Modifiers

Published on: September 20, 2018

S Basak1, V Nagaraja

  • 1Microbiology and Cell Biology Department, Indian Institute of Science, Bangalore, 560 012, India.

Journal of Molecular Biology
|December 5, 1998
PubMed

Insights

Bacteriophage Mu protein C activates the mom gene by distorting and unwinding DNA, improving RNA polymerase binding. This mechanism optimizes transcription of the essential mom gene for phage DNA modification.

Area of Science:

  • Molecular Biology
  • Genetics
  • Virology

Background:

  • The bacteriophage Mu mom gene is crucial for DNA modification.
  • Transcriptional regulation of the mom gene is mediated by the transactivator protein C.
  • The mom promoter (Pmom) is characterized by weak -10 and -35 elements and a suboptimal spacer, potentially hindering RNA polymerase binding.

Purpose of the Study:

  • To elucidate the mechanism by which protein C activates transcription at the Pmom promoter.
  • To investigate how protein C overcomes the suboptimal promoter structure to facilitate transcription.

Main Methods:

  • In vivo dimethyl sulfate footprinting to analyze protein C interactions with the mom regulatory region.
  • Coupled topoisomerase assay to assess DNA unwinding induced by protein C.

Main Results:

  • Protein C binding induces asymmetric distortion of its specific site within the mom regulatory region.
  • Protein C induces DNA unwinding, localized to the 3' flanking region of the C binding site, overlapping the -35 element.
  • These structural changes likely reorient promoter elements for enhanced RNA polymerase occupancy.

Conclusions:

  • Protein C acts as a transcriptional activator by inducing DNA torsional changes (unwinding) at the Pmom promoter.
  • This mechanism facilitates RNA polymerase binding to the weak promoter elements, enabling efficient mom gene transcription.
  • The findings provide insight into phage gene regulation and promoter activation strategies.

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