Accumulation of polyadenylated mRNA, Pab1p, eIF4E, and eIF4G with P-bodies in Saccharomyces cerevisiae.
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.
Brengues
Muriel
M
Department of Molecular and Cellular Biology, Howard Hughes Medical Institute, University of Arizona, Tucson, AZ 85721-0106, USA.
Parker
Roy
R
D022003:Cell Nucleus Structures / Q000378:metabolism*; D004722:Endoribonucleases; D039561:Eukaryotic Initiation Factor-4E / Q000378:metabolism*; D039603:Eukaryotic Initiation Factor-4G / Q000378:metabolism*; D005947:Glucose / Q000172:deficiency; D039102:Poly(A)-Binding Proteins / Q000378:metabolism*; D014176:Protein Biosynthesis; D034443:RNA Transport; D012333:RNA, Messenger / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*
D039561:Eukaryotic Initiation Factor-4E; D039603:Eukaryotic Initiation Factor-4G; D039102:Poly(A)-Binding Proteins; D012333:RNA, Messenger; D029701:Saccharomyces cerevisiae Proteins; C450100:pab1 protein, S cerevisiae; C400572:DCP2 protein, S cerevisiae; D004722:Endoribonucleases; D005947:Glucose