Technical Data
0004-22
4E Binding Protein 1 (Protein Synthesis Initiation Factor 4E Binding Protein, eIF-4EBP1, PHAS-1, PHAS-I, Eukaryotic Translation Initiation Factor BP)
Description:
PHAS-I, also known as eIF4E-BP1 and PHAS-II,-III (eIF4E-BP2, 3), are members of a family of proteins that regulate eukaryotic translation initiation which is mediated by the cap structure (m7GpppN, where N=any nucleotide) present at the 5 end of all cellular mRNAs, except organellar (1). The m7 cap is essential for the translation of most mRNA because it directs the translation machinery of the 5 end of the mRNA via its interaction with the cap binding protein, the translation initiation factor 4E(eIF4E) (2). eIF4E plays an principal role in determining global translation rates because its interaction with the cap facilitates the binding of the ribosome to the mRNA. Consistent with this role, eIF4E is required for cell cycle progression, exhibits anti-apoptotic activity and when overexpressed transforms cells (2). Interaction with PHAS proteins prevents incorporation of eIF4E into an active translation initiation complex and inhibits cap-dependent translation. However, this inhibitory effect is alleviated following phosphorylation of the PHAS proteins by a P13K-dependent pathway, involving signaling by the anti-apoptotic kinase Akt/PKB, as well as FRAP/mTOR (2). Rat PHAS-I has 117 amino acids with a apparent molecular weight of 22kD and is 93% identical to eIF-4E-BPI cloned from human placenta (3, 4). PHAS-I and II were found to have overlapping but different patterns of expression in tissues. PHAS-I is expressed in a wide variety of cell types with the highest being in two of the most insulin-responsive tissues, adipocytes and skeletal muscle (3). Both PHAS proteins are phosphorylated in response to insulin or growth factors such as EGF, PDGF and IGF-1. Increasing cAMP in cells promotes dephosphorylation of both PHAS-I and PHAS-II but that regulation of the two protein differ because PHAS-II, unlike PHAS-I is readily phosphorylated by PKA (5). The PHAS-I initiation factor has 28 phosphorylation sites and is multiply phosphorylated by insulin-stimulated protein kinase(s) resulting in 810 phosphorylated isoforms in exponentially growing cells. Changes occur in the expression of these isoforms in response to stresses such as heat shock, and this may contribute to translation repression (6).

Applications:
Western Blot (Colorimetric): 4ug/ml
Gel Shift
Optimal dilutions to be determined by researcher.
TypeIsotypeCloneGrade
PabIgGAffinity Purified
SizeStorageShippingSourceHost
25ug-20CBlue IceRatRabbit
Concentration:
Immunogen:
An 18 residue synthetic peptide SPEDKRAGGEESQFEMDI based on the human PHAS-I (residues 101-118) and the peptide coupled to KLH. This sequence is identical to rat and mouse PHAS- I over these residues.
Purity:
Purified by immunoaffinity chromatography.
Form
Supplied as a liquid in borate buffered saline, pH 8.4 25mM sodium borate, 100mM boric acid, 75mM sodium chloride, 5mM EDTA (disodium salt).
Specificity:
This immunoaffinity purified antibody detects multiple bands (19-25kD), corresponding to the apparent molecular mass of the various phosphorylation states of recombinant and native PHAS-I protein on SDS-PAGE immunoblots, in samples from human, mouse and rat. This antibody has been shown to react with purified recombinant PHAS-I rat protein on immunoblot analysis. This antibody provides a simple read-out for PKB (Akt) activity in vivo through the use of gel-shift assays. Antibody specificity has been confirmed in Western blot peptide competition studies.
Intended for research use only. Not for use in human, therapeutic, or diagnostic applications.
1. Poulin, F., Gingras, A. C., Olsen, H., Chevallier, S. and Sonenberg, N (1998) J. Biol. Chem. 273: 14001-14007. 2. Raught, B and Gingras, A. C. (1999) Int. J. Biochem Cell Biol. 31: 43-57. 3. Hu, C., Pang, S.,Kong, X., Velleca, M. and Lawrence Jr., J. C. PNAS USA 91: 3730-3734. 4. Pause, A., Belsham, G. J., Gingras, A. C.,Donze, O., Lin, T. A. Lawrence, Jr. and Sonenberg, N. (1994) Nature 371: 762-767. 5. Lawrence, J. C., Fadden, P., Haystead, T. A. and Lin, T. A. (1997) Adv. Enzyme regul. 37: 239-267. 6. Duncan, R.F. and Song, H. J (1999) Eur. J. Biochem. 265: 728-743.