Phospho-eIF4B (Ser422) Antibod

3591:

Western Blotting

Phospho-eIF4B (Ser422) Antibody detects eIF4B only when phosphorylated at Ser422.

Polyclonal antibodies are produced by immunizing animals with a synthetic phosphopeptide corresponding to residues surrounding Ser422 of human eIF4B. Antibodies are purified by protein A and peptide affinity chromatography.

Western Blotting

Western blot analysis of extracts from HeLa cells using Phospho-eIF4B (Ser422) Antibody (upper) or eIF4B Antibody #3592 (lower). 48 hours following siRNA transfection, cells were treated with Rapamycin (50 nM) and U0126 (10 µM) as indicated.

Eukaryotic initiation factor 4B (eIF4B) is thought to assist the eIF4F complex in translation initiation. In plants, eIF4B is known to interact with the poly-(A) binding protein, increasing its poly-(A) binding activity (1). Heat shock and serum starvation cause dephosphorylation of eIF4B at multiple sites with kinetics similar to those of the corresponding inhibition of translation, while phosphorylation of eIF4B following insulin treatment correlates well with an observed increase in translation (2-5). Multiple kinases, including p70 S6 kinase, can phosphorylate eIF4B in vitro , and at least one serum-inducible eIF4B phosphorylation site is sensitive to rapamycin and LY294002 (6). Recently, Ser406 was identified as a novel phosphorylation site regulated by mitogens (7), and the phosphorylation of this site is dependent on MEK and mTOR activity (7). This phosphorylation is shown to be essential for the translational activity of eIF4B (7).

p70 S6 Kinase has been shown to phosphorylate eIF4B at the rapamycin-sensitive site Ser422 in vivo, and a Ser422Ala mutant of eIF4B shows deminished activity in an in vitro translation assay (7).

1. Le, H. et al. (1997) J. Biol. Chem. 272, 16247-16255.
2. Duncan, R.F. and Hershey, J.W. (1989) J. Cell Biol. 109, 1467-1481.
3. Duncan, R.F. and Hershey, J.W. (1984) J. Biol. Chem. 259, 11882-11889.
4. Duncan, R. and Hershey, J.W. (1985) J. Biol. Chem. 260, 5493-5497.
5. Manzella, J.M. et al. (1991) J. Biol. Chem. 266, 2383-2389.
6. Gingras, A.C. et al. (2001) Genes Dev. 15, 807-826.
7. van Gorp, A.G. et al. (2009) Oncogene 28, 95-106.
8. Raught, B. et al. (2004) EMBO J. 23, 1761-1769.

• Peiretti, F. et al. (2004) Serum- and mitogen-responsive phosphorylation of eukaryotic translation initiation factor 4B (eIF4B) Ser422 is modulated by ribosomal S6 kinases. EMBO J. 23, 1761-1769. Applications: Western Blotting

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