Accumulation of polyadenylated mRNA, Pab1p, eIF4E, and eIF4G with P-bodies in Saccharomyces cerevisiae

Mol Biol Cell. 2007 Jul;18(7):2592-602. doi: 10.1091/mbc.e06-12-1149. Epub 2007 May 2.

Abstract

Recent experiments have shown that mRNAs can move between polysomes and P-bodies, which are aggregates of nontranslating mRNAs associated with translational repressors and the mRNA decapping machinery. The transitions between polysomes and P-bodies and how the poly(A) tail and the associated poly(A) binding protein 1 (Pab1p) may affect this process are unknown. Herein, we provide evidence that poly(A)(+) mRNAs can enter P-bodies in yeast. First, we show that both poly(A)(-) and poly(A)(+) mRNA become translationally repressed during glucose deprivation, where mRNAs accumulate in P-bodies. In addition, both poly(A)(+) transcripts and/or Pab1p can be detected in P-bodies during glucose deprivation and in stationary phase. Cells lacking Pab1p have enlarged P-bodies, suggesting that Pab1p plays a direct or indirect role in shifting the equilibrium of mRNAs away from P-bodies and into translation, perhaps by aiding in the assembly of a type of mRNP within P-bodies that is poised to reenter translation. Consistent with this latter possibility, we observed the translation initiation factors (eIF)4E and eIF4G in P-bodies at a low level during glucose deprivation and at high levels in stationary phase. Moreover, Pab1p exited P-bodies much faster than Dcp2p when stationary phase cells were given fresh nutrients. Together, these results suggest that polyadenylated mRNAs can enter P-bodies, and an mRNP complex including poly(A)(+) mRNA, Pab1p, eIF4E, and eIF4G2 may represent a transition state during the process of mRNAs exchanging between P-bodies and translation.

Publication types

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

MeSH terms

  • Cell Nucleus Structures / metabolism*
  • Endoribonucleases
  • Eukaryotic Initiation Factor-4E / metabolism*
  • Eukaryotic Initiation Factor-4G / metabolism*
  • Glucose / deficiency
  • Poly(A)-Binding Proteins / metabolism*
  • Protein Biosynthesis
  • RNA Transport
  • RNA, Messenger / metabolism
  • Saccharomyces cerevisiae / cytology
  • Saccharomyces cerevisiae / metabolism*
  • Saccharomyces cerevisiae Proteins / metabolism*

Substances

  • Eukaryotic Initiation Factor-4E
  • Eukaryotic Initiation Factor-4G
  • Poly(A)-Binding Proteins
  • RNA, Messenger
  • Saccharomyces cerevisiae Proteins
  • pab1 protein, S cerevisiae
  • DCP2 protein, S cerevisiae
  • Endoribonucleases
  • Glucose