Termination of mammalian rDNA replication: polar arrest of replication fork movement by transcription termination factor TTF-I

Cell. 1997 Aug 8;90(3):559-67. doi: 10.1016/s0092-8674(00)80515-2.


A replication fork barrier (RFB) at the 3' end of eukaryotic ribosomal RNA genes blocks bidirectional fork progression and limits DNA replication to the same direction as transcription. We have reproduced the RFB in vitro in HeLa cell extracts using 3' terminal murine rDNA fused to an SV40 origin-based vector. The RFB is polar and modularly organized, requiring both the Sal box transcription terminator and specific flanking sequences. Mutations within the terminator element, depletion of the RNA polymerase I-specific transcription termination factor TTF-I, or deletion of the termination domain of TTF-I abolishes RFB activity. Thus, the same factor that blocks elongating RNA polymerase I prevents head-on collision between the DNA replication apparatus and the transcription machinery.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 3T3 Cells
  • Animals
  • DNA Replication*
  • DNA, Ribosomal / biosynthesis*
  • DNA, Ribosomal / chemistry
  • DNA-Binding Proteins / metabolism*
  • HeLa Cells
  • Humans
  • Mammals
  • Mice
  • Mutagenesis, Site-Directed
  • RNA Polymerase I / metabolism
  • RNA, Ribosomal / biosynthesis
  • RNA, Ribosomal / genetics
  • Recombinant Proteins / metabolism
  • Sequence Deletion
  • Terminator Regions, Genetic*
  • Transcription Factors
  • Transfection


  • DNA, Ribosomal
  • DNA-Binding Proteins
  • RNA, Ribosomal
  • Recombinant Proteins
  • TTF1 protein, human
  • Transcription Factors
  • Ttf1 protein, mouse
  • RNA Polymerase I