Distinct pathways for snoRNA and mRNA termination

Mol Cell. 2006 Dec 8;24(5):723-734. doi: 10.1016/j.molcel.2006.11.011.


Transcription termination at mRNA genes is linked to polyadenylation. Cleavage at the poly(A) site generates an entry point for the Rat1/Xrn2 exonuclease, which degrades the downstream transcript to promote termination. Small nucleolar RNAs (snoRNAs) are also transcribed by RNA polymerase II but are not polyadenylated. Chromatin immunoprecipitation experiments show that polyadenylation factors and Rat1 localize to snoRNA genes, but mutations that disrupt poly(A) site cleavage or Rat1 activity do not lead to termination defects at these genes. Conversely, mutations of Nrd1, Sen1, and Ssu72 affect termination at snoRNAs but not at several mRNA genes. The exosome complex was required for 3' trimming, but not termination, of snoRNAs. Both the mRNA and snoRNA pathways require Pcf11 but show differential effects of individual mutant alleles. These results suggest that in yeast the transcribing RNA polymerase II can choose between two distinct termination mechanisms but keeps both options available during elongation.

Publication types

  • Comparative Study
  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Blotting, Northern
  • Chromatin Immunoprecipitation
  • DNA Helicases
  • DNA Polymerase II / metabolism
  • Exoribonucleases / genetics
  • Exoribonucleases / metabolism
  • Fungal Proteins / metabolism
  • Nuclear Proteins / metabolism
  • Oligonucleotide Array Sequence Analysis
  • RNA Helicases
  • RNA, Messenger / genetics
  • RNA, Messenger / metabolism*
  • RNA, Small Nucleolar / genetics
  • RNA, Small Nucleolar / metabolism*
  • RNA-Binding Proteins / metabolism
  • Ribonucleoproteins / metabolism
  • Saccharomyces cerevisiae
  • Saccharomyces cerevisiae Proteins / genetics
  • Saccharomyces cerevisiae Proteins / metabolism
  • Transcription, Genetic


  • Fungal Proteins
  • NAB3 protein, S cerevisiae
  • NRD1 protein, S cerevisiae
  • Nuclear Proteins
  • RNA, Messenger
  • RNA, Small Nucleolar
  • RNA-Binding Proteins
  • Ribonucleoproteins
  • Saccharomyces cerevisiae Proteins
  • RAT1 protein, S cerevisiae
  • DNA Polymerase II
  • Exoribonucleases
  • SEN1 protein, S cerevisiae
  • DNA Helicases
  • RNA Helicases