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In Vitro Selection of Engineered Transcriptional Repressors for Targeted Epigenetic Silencing
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Multiple mechanisms contribute to inhibit transcription in response to DNA damage

George F Heine1, Andrew A Horwitz, Jeffrey D Parvin

  • 1Department of Biomedical Informatics and the Comprehensive Cancer Center, Ohio State University, Columbus, OH 43210, USA.

The Journal of Biological Chemistry
|February 19, 2008
PubMed

Insights

Cellular DNA damage triggers distinct transcriptional repression pathways. UV irradiation, unlike H2O2, induces slower inhibition dependent on proteasomes and new protein synthesis, highlighting diverse DNA repair responses.

Area of Science:

  • Molecular Biology
  • Cellular Biology
  • Biochemistry

Background:

  • Cellular DNA damage activates signaling pathways that regulate gene expression.
  • RNA polymerase II (RNAPII) phosphorylation and ubiquitination are key events in transcriptional repression.
  • Understanding the mechanisms of transcriptional regulation during DNA damage is crucial for cellular repair.

Purpose of the Study:

  • To investigate the distinct pathways of transcriptional repression following different types of DNA damage.
  • To elucidate the role of proteasomes, new protein synthesis, and P-TEFb kinase in UV-induced transcriptional inhibition.
  • To understand how global transcription is repressed to facilitate DNA damage repair.

Main Methods:

  • Treatment of cells with hydrogen peroxide (H2O2) and UV irradiation to induce DNA damage.
  • Analysis of RNA polymerase II (RNAPII) phosphorylation and ubiquitination status.
  • Assessment of transcriptional inhibition and restoration kinetics.
  • Investigation of the role of proteasomes and new protein synthesis in transcriptional repression.
  • Examination of P-TEFb kinase activity in regulating RNAPII.

Main Results:

  • Two distinct pathways for transcriptional repression were identified, dependent on the type of DNA damage.
  • H2O2 treatment caused rapid inhibition and restoration of transcription.
  • UV irradiation led to slower transcriptional inhibition, depletion of unphosphorylated RNAPII, and required proteasome activity and new protein synthesis.
  • RNAPII activity and ubiquitination were modulated by P-TEFb kinase-mediated phosphorylation.

Conclusions:

  • Cellular responses to DNA damage involve multiple, distinct pathways for global transcriptional repression.
  • The specific DNA damage type dictates the mechanism and kinetics of transcriptional shutdown.
  • These repression mechanisms likely serve to prevent interference with DNA repair processes.

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