General RNA-binding proteins have a function in poly(A)-binding protein-dependent translation.
The interaction between the poly(A)-binding protein (PABP) and eukaryotic translational initiation factor 4G (eIF4G), which brings about circularization of the mRNA, stimulates translation. General RNA-binding proteins affect translation, but their role in mRNA circularization has not been studied before. Here, we demonstrate that the major mRNA ribonucleoprotein YB-1 has a pivotal function in the regulation of eIF4F activity by PABP. In cell extracts, the addition of YB-1 exacerbated the inhibition of 80S ribosome initiation complex formation by PABP depletion. Rabbit reticulocyte lysate in which PABP weakly stimulates translation is rendered PABP-dependent after the addition of YB-1. In this system, eIF4E binding to the cap structure is inhibited by YB-1 and stimulated by a nonspecific RNA. Significantly, adding PABP back to the depleted lysate stimulated eIF4E binding to the cap structure more potently if this binding had been downregulated by YB-1. Conversely, adding nonspecific RNA abrogated PABP stimulation of eIF4E binding. These data strongly suggest that competition between YB-1 and eIF4G for mRNA binding is required for efficient stimulation of eIF4F activity by PABP.
Svitkin
Yuri V
YV
Department of Biochemistry and Goodman Cancer Center, McGill University, Montreal, Quebec, Canada.
Evdokimova
Valentina M
VM
Brasey
Ann
A
Pestova
Tatyana V
TV
Fantus
Daniel
D
Yanagiya
Akiko
A
Imataka
Hiroaki
H
Skabkin
Maxim A
MA
Ovchinnikov
Lev P
LP
Merrick
William C
WC
Sonenberg
Nahum
N
D000818:Animals; D002457:Cell Extracts; D002460:Cell Line; D004268:DNA-Binding Proteins / Q000378:metabolism*; D039562:Eukaryotic Initiation Factor-4F / Q000378:metabolism*; D051379:Mice; D008954:Models, Biological; D009687:Nuclear Proteins / Q000378:metabolism*; D039102:Poly(A)-Binding Proteins / Q000378:metabolism*; D014176:Protein Biosynthesis; D011817:Rabbits; D051840:Y-Box-Binding Protein 1
D002457:Cell Extracts; D004268:DNA-Binding Proteins; D039562:Eukaryotic Initiation Factor-4F; D009687:Nuclear Proteins; D039102:Poly(A)-Binding Proteins; D051840:Y-Box-Binding Protein 1; C070856:YBX1 protein, human