Trf4 and Trf5 proteins of Saccharomyces cerevisiae exhibit poly(A) RNA polymerase activity but no DNA polymerase activity

Mol Cell Biol. 2005 Nov;25(22):10183-9. doi: 10.1128/MCB.25.22.10183-10189.2005.


The Saccharomyces cerevisiae Trf4 and Trf5 proteins are members of a distinct family of eukaryotic DNA polymerase beta-like nucleotidyltransferases, and a template-dependent DNA polymerase activity has been reported for Trf4. To define the nucleotidyltransferase activities associated with Trf4 and Tr5, we purified these proteins from yeast cells and show that whereas both proteins exhibit a robust poly(A) polymerase activity, neither of them shows any evidence of a DNA polymerase activity. The poly(A) polymerase activity, as determined for Trf4, is strictly Mn2+ dependent and highly ATP specific, incorporating AMP onto the free 3'-hydroxyl end of an RNA primer. Unlike the related poly(A) polymerases from other eukaryotes, which are located in the cytoplasm and regulate the stability and translation efficiency of specific mRNAs, the Trf4 and Trf5 proteins are nuclear, and a multiprotein complex associated with Trf4 has been recently shown to polyadenylate a variety of misfolded or inappropriately expressed RNAs which activate their degradation by the exosome. To account for the effects of Trf4/Trf5 proteins on the various aspects of DNA metabolism, including chromosome condensation, DNA replication, and sister chromatid cohesion, we suggest an additional and essential role for the Trf4 and Trf5 protein complexes in generating functional mRNA poly(A) tails in the nucleus.

Publication types

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

MeSH terms

  • Adenosine Triphosphate / chemistry
  • Binding Sites
  • Cell Nucleus / metabolism
  • Chromosomes / ultrastructure
  • Cytoplasm / metabolism
  • DNA / chemistry
  • DNA Primers / chemistry
  • DNA-Directed DNA Polymerase / chemistry*
  • DNA-Directed DNA Polymerase / metabolism
  • DNA-Directed DNA Polymerase / physiology
  • DNA-Directed RNA Polymerases / chemistry
  • DNA-Directed RNA Polymerases / physiology*
  • Dose-Response Relationship, Drug
  • Guanosine Triphosphate / chemistry
  • Manganese / chemistry
  • Mutation
  • Open Reading Frames
  • Phenotype
  • Polynucleotide Adenylyltransferase / metabolism*
  • Protein Binding
  • Protein Folding
  • Protein Structure, Tertiary
  • RNA / chemistry
  • RNA, Messenger / metabolism
  • Saccharomyces cerevisiae / metabolism*
  • Saccharomyces cerevisiae Proteins / chemistry
  • Saccharomyces cerevisiae Proteins / metabolism
  • Saccharomyces cerevisiae Proteins / physiology*
  • Sister Chromatid Exchange


  • DNA Primers
  • RNA, Messenger
  • Saccharomyces cerevisiae Proteins
  • Manganese
  • RNA
  • Guanosine Triphosphate
  • Adenosine Triphosphate
  • DNA
  • Polynucleotide Adenylyltransferase
  • DNA-Directed RNA Polymerases
  • Trf5 protein, S cerevisiae
  • DNA-Directed DNA Polymerase
  • PAP2 protein, S cerevisiae