EIF4EBP1

Phosphorylated 4E-BP1 is thought to be a marker of upstream signaling (mTOR) activation. 4E-BP1 has seven phospho-sites, the three most important of which are the initiation site Thr 37/Thr 46, the second site Thr 70, and the final site Ser65. Moreover, phosphorylation of Ser 65 and Thr 70 alone was not sufficient to block the inhibition of mRNA translation by 4E-BP1, suggesting that multiple phosphorylation events must be combined to increase the rate of protein synthesis.^[7]

This gene encodes one member of a family of translation repressor proteins. The protein directly interacts with eukaryotic translation initiation factor 4E (eIF4E), which is a limiting component of the multisubunit complex that recruits 40S ribosomal subunits to the 5' end of mRNAs. Interaction of this protein with eIF4E inhibits complex assembly and represses translation. This protein is phosphorylated in response to various signals including UV irradiation and insulin signaling, resulting in its dissociation from eIF4E and activation of cap-dependent mRNA translation.^[8]

High level of phosphorylated 4E-BP1 has been widely reported in human cancers, and is associated with a worse outcome in several malignancies.^[9]

EIF4EBP1 has been shown to interact with:

• EIF4E,^{[10][11][12][13][14][15][16][17][18][19][20][21][22]}
• KIAA1303,^{[14][23][24][25][26][27][28][29]} and
• Mammalian target of rapamycin (mTOR).^{[23][24][25][26][30][31][32][33]}