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Transcriptional pausing, arrest, and readthrough at the adenovirus major late attenuation site

D K Hawley1, D K Wiest, M S Holtz

  • 1Institute of Molecular Biology, University of Oregon, Eugene 97403.

Cellular & Molecular Biology Research
|January 1, 1993
PubMed

Insights

RNA polymerase II (pol II) elongation can be blocked at specific sites. Elongation factor SII promotes readthrough of these arrest sites by enhancing pol II

Area of Science:

  • Molecular Biology
  • Gene Expression
  • Biochemistry

Background:

  • RNA polymerase II (pol II) transcription can arrest at specific DNA sequences, halting elongation.
  • Adenovirus major late promoter exhibits an attenuation site causing pol II arrest in vitro and in vivo.
  • Elongation factor SII (SII) is known to promote readthrough of arrest sites.

Purpose of the Study:

  • To investigate the mechanism by which Elongation factor SII (SII) promotes readthrough of RNA polymerase II (pol II) arrest sites.
  • To test the hypothesis that SII enhances pol II's 3' to 5' exonuclease activity to facilitate readthrough.
  • To examine the role of polymerase pause duration at attenuation sites in the efficiency of arrest.

Main Methods:

  • In vitro transcription assays using adenovirus major late promoter.
  • Analysis of RNA polymerase II (pol II) ternary complex stability and elongation.
  • Investigating the 3' to 5' exonuclease activity of pol II stimulated by Elongation factor SII (SII).

Main Results:

  • Elongation factor SII (SII) stimulates a 3' to 5' exonuclease activity of RNA polymerase II (pol II).
  • SII appears to promote readthrough of arrest sites by enabling cycles of RNA removal and resynthesis.
  • The duration of polymerase pausing at the attenuation site correlates with the efficiency of arrest.

Conclusions:

  • The study supports a model where Elongation factor SII (SII) facilitates RNA polymerase II (pol II) readthrough via enhanced exonuclease activity.
  • SII-mediated exonuclease activity may allow polymerases to backtrack and resynthesize RNA, overcoming arrest sites.
  • Pause duration is a critical factor influencing the likelihood of RNA polymerase II (pol II) arrest.

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