Journal
EMBO JOURNAL
Volume 25, Issue 12, Pages 2781-2791Publisher
WILEY
DOI: 10.1038/sj.emboj.7601166
Keywords
crosstalk; eIF4B; phosphorylation; signaling; translation
Categories
Funding
- NCI NIH HHS [R37 CA46595, R37 CA046595] Funding Source: Medline
- NIGMS NIH HHS [GM22135, R01 GM5140, R01 GM022135] Funding Source: Medline
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The eukaryotic translation initiation factor 4B ( eIF4B) plays a critical role in recruiting the 40S ribosomal subunit to the mRNA. In response to insulin, eIF4B is phosphorylated on Ser422 by S6K in a rapamycin-sensitive manner. Here we demonstrate that the p90 ribosomal protein S6 kinase ( RSK) phosphorylates eIF4B on the same residue. The relative contribution of the RSK and S6K modules to the phosphorylation of eIF4B is growth factor-dependent, and the two phosphorylation events exhibit very different kinetics. The S6K and RSK proteins are members of the AGC protein kinase family, and require PDK1 phosphorylation for activation. Consistent with this requirement, phosphorylation of eIF4B Ser422 is abrogated in PDK1 null embryonic stem cells. Phosphorylation of eIF4B on Ser422 by RSK and S6K is physiologically significant, as it increases the interaction of eIF4B with the eukaryotic translation initiation factor 3.
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