Selective Modification of Eukaryotic Initiation Factor 4F (eIF4F) at the Onset of Cell Differentiation: Recruitment of eIF4GII and Long-Lasting Phosphorylation of eIF4E

AUTOR(ES)

Caron, Sandrine

FONTE

American Society for Microbiology

RESUMO

mRNA translation is mainly regulated at the level of initiation, a process that involves the synergistic action of the 5′ cap structure and the 3′ poly(A) tail at the ends of eukaryotic mRNA. The eukaryote initiation factor 4G(eIF4G) is a pivotal scaffold protein that forms a critical link between mRNA cap structure, poly(A) tail, and the small ribosomal subunit. There are two functional homologs of eIF4G in mammals, the original eIF4G, renamed eIF4GI, and eIF4GII that functionally complements eIF4GI. To date, biochemical and functional analysis have not identified differential activities for eIF4GI and eIF4GII. In this report, we demonstrate that eIF4GII, but not eIF4GI, is selectively recruited to capped mRNA at the onset of cell differentiation. This recruitment is coincident with a strong and long-lasting phosphorylation of eIF4E and the release of 4E-BP1, a suppressor of eIF4E function, from the cap structure, without a concomitant change in 4E-BP1's phosphorylation. Our data further indicate that cytokines such as thrombopoietin can differentially regulate eIF4GI/II activities. These results provide the first evidence that eIF4GI/II does fulfill selective roles in mammalian cells.

Documentos Relacionados

• Human Rhinovirus 2A Proteinase Cleavage Sites in Eukaryotic Initiation Factors (eIF) 4GI and eIF4GII Are Different
• Eukaryotic Initiation Factor 4GII (eIF4GII), but Not eIF4GI, Cleavage Correlates with Inhibition of Host Cell Protein Synthesis after Human Rhinovirus Infection
• Modification of eukaryotic initiation factor 4F during infection by influenza virus.
• Mechanical influences on long-lasting human muscle fatigue and delayed-onset pain.
• Kindling produces long-lasting and selective changes in gene expression of hippocampal neurons.