Strand separation establishes a sustained lock at the Tus-Ter replication fork barrier

Bojk A. Berghuis, David Dulin, Zhi Qiang Xu, Theo Van Laar, Bronwen Cross, Richard Janissen, Slobodan Jergic, Nicholas E. Dixon, Martin Depken, Nynke H. Dekker

Research output: Contribution to journalArticleScientificpeer-review

17 Citations (Scopus)
16 Downloads (Pure)

Abstract

The bidirectional replication of a circular chromosome by many bacteria necessitates proper termination to avoid the head-on collision of the opposing replisomes. In Escherichia coli, replisome progression beyond the termination site is prevented by Tus proteins bound to asymmetric Ter sites. Structural evidence indicates that strand separation on the blocking (nonpermissive) side of Tus-Ter triggers roadblock formation, but biochemical evidence also suggests roles for protein-protein interactions. Here DNA unzipping experiments demonstrate that nonpermissively oriented Tus-Ter forms a tight lock in the absence of replicative proteins, whereas permissively oriented Tus-Ter allows nearly unhindered strand separation. Quantifying the lock strength reveals the existence of several intermediate lock states that are impacted by mutations in the lock domain but not by mutations in the DNA-binding domain. Lock formation is highly specific and exceeds reported in vivo efficiencies. We postulate that protein-protein interactions may actually hinder, rather than promote, proper lock formation.

Original languageEnglish
Pages (from-to)579-585
Number of pages7
JournalNature Chemical Biology
Volume11
DOIs
Publication statusPublished - 2015

Keywords

  • DNA-binding proteins
  • nucleic acids
  • single-molecule biophysics

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