Effects of Transcription Elongation Rate and Xrn2 Exonuclease Activity on RNA Polymerase II Termination Suggest Widespread Kinetic Competition

Nova Fong, Kristopher Brannan, Benjamin Erickson, Hyunmin Kim, Michael A. Cortazar, Ryan M. Sheridan, Tram Nguyen, Shai Karp, David L. Bentley

Research output: Contribution to journalArticlepeer-review

110 Scopus citations

Abstract

The torpedo model of transcription termination asserts that the exonuclease Xrn2 attacks the 5'PO4-end exposed by nascent RNA cleavage and chases down the RNA polymerase. We tested this mechanism using a dominant-negative human Xrn2 mutant and found that it delayed termination genome-wide. Xrn2 nuclease inactivation caused strong termination defects downstream of most poly(A) sites and modest delays at some histone and U snRNA genes, suggesting that the torpedo mechanism is not limited to poly(A) site-dependent termination. A central untested feature of the torpedo model is that there is kinetic competition between the exonuclease and the pol II elongation complex. Using pol II rate mutants, we found that slow transcription robustly shifts termination upstream, and fast elongation extends the zone of termination further downstream. These results suggest that kinetic competition between elongating pol II and the Xrn2 exonuclease is integral to termination of transcription on most human genes.

Original languageEnglish (US)
Pages (from-to)256-267
Number of pages12
JournalMolecular Cell
Volume60
Issue number2
DOIs
StatePublished - Oct 15 2015

ASJC Scopus subject areas

  • Molecular Biology
  • Cell Biology

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