Efficient termination of transcription by RNA polymerase I requires the 5' exonuclease Rat1 in yeast

Genes Dev. 2008 Apr 15;22(8):1069-81. doi: 10.1101/gad.463708.

Abstract

During transcription termination by RNA polymerase II on protein-coding genes, the nuclear 5' exonuclease Rat1/Xrn2 degrades the nascent transcript downstream from the polyadenylation site and "torpedoes" the polymerase. We report that the activity of Rat1 is also required for efficient termination by RNA polymerase I (Pol I) on the rDNA. In strains lacking catalytically active Rat1 or its cofactor Rai1, Pol I reads through the major, "Reb1-dependent" terminator (T1) but stops downstream at the "fail-safe" terminator (T2) and replication fork barrier (RFB). The absence of both Rat1 and the RFB-binding protein Fob1 increased Pol I read-through of T2 and the RFB. We propose that cotranscriptional cleavage of the pre-rRNA by the endonuclease Rnt1 generates a loading site for the Rat1/Rai1 complex, which then degrades the nascent transcript. When Rat1 catches Pol I, which is predicted to be paused at T1, transcription is terminated.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • DNA, Ribosomal / metabolism
  • Exoribonucleases / metabolism*
  • Models, Biological
  • Models, Genetic
  • Nuclear Proteins / metabolism
  • RNA Polymerase I / metabolism*
  • RNA, Ribosomal, 5.8S / metabolism
  • RNA-Binding Proteins
  • Saccharomyces cerevisiae / enzymology*
  • Saccharomyces cerevisiae / metabolism
  • Saccharomyces cerevisiae Proteins / metabolism*
  • Terminator Regions, Genetic / genetics*
  • Transcription, Genetic*

Substances

  • DNA, Ribosomal
  • Nuclear Proteins
  • RNA, Ribosomal, 5.8S
  • RNA-Binding Proteins
  • Rai1 protein, S cerevisiae
  • Saccharomyces cerevisiae Proteins
  • RAT1 protein, S cerevisiae
  • RNA Polymerase I
  • Exoribonucleases
  • XRN1 protein, S cerevisiae