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A nuclear 3'-5' exonuclease involved in mRNA degradation interacts with Poly(A) polymerase and the hnRNA protein Npl3p.

Inactivation of poly(A) polymerase (encoded by PAP1) in Saccharomyces cerevisiae cells carrying the temperature-sensitive, lethal pap1-1 mutation results in reduced levels of poly(A)(+) mRNAs. Genetic selection for suppressors of pap1-1 yielded two recessive, cold-sensitive alleles of the gene RRP6. These suppressors, rrp6-1 and rrp6-2, as well as a deletion of RRP6, allow growth of pap1-1 strains at high temperature and partially restore the levels of poly(A)(+) mRNA in a manner distinct from the cytoplasmic mRNA turnover pathway and without slowing a rate-limiting step in mRNA decay. Subcellular localization of an Rrp6p-green fluorescent protein fusion shows that the enzyme residues in the nucleus. Phylogenetic analysis and the nature of the rrp6-1 mutation suggest the existence of a highly conserved 3'-5' exonuclease core domain within Rrp6p. As predicted, recombinant Rrp6p catalyzes the hydrolysis of a synthetic radiolabeled RNA in a manner consistent with a 3'-5' exonucleolytic mechanism. Genetic and biochemical experiments indicate that Rrp6p interacts with poly(A) polymerase and with Npl3p, a poly(A)(+) mRNA binding protein implicated in pre-mRNA processing and mRNA nuclear export. These findings suggest that Rrp6p may interact with the mRNA polyadenylation system and thereby play a role in a nuclear pathway for the degradation of aberrantly processed precursor mRNAs.

Pubmed ID: 10611239


  • Burkard KT
  • Butler JS


Molecular and cellular biology

Publication Data

January 27, 2000

Associated Grants

  • Agency: NIGMS NIH HHS, Id: GM 59898

Mesh Terms

  • Amino Acid Sequence
  • Catalytic Domain
  • Cell Nucleus
  • Exoribonucleases
  • Exosome Multienzyme Ribonuclease Complex
  • Fungal Proteins
  • Genes, Fungal
  • Half-Life
  • Molecular Sequence Data
  • Mutation
  • Nuclear Proteins
  • Polynucleotide Adenylyltransferase
  • Protein Binding
  • RNA Processing, Post-Transcriptional
  • RNA Stability
  • RNA, Fungal
  • RNA, Heterogeneous Nuclear
  • RNA, Messenger
  • RNA-Binding Proteins
  • Recombinant Fusion Proteins
  • Saccharomyces cerevisiae
  • Saccharomyces cerevisiae Proteins
  • Sequence Alignment
  • Suppression, Genetic
  • Temperature