The 4E-BP Antibody Sampler Kit provides an economical means to investigate regulation of cap-dependent translation within the cell. The kit contains primary and secondary antibodies to perform two Western blots with each antibody.
Specificity / Sensitivity
Phospho-4E-BP1 (Thr37/46) Rabbit mAb detects endogenous levels of 4E-BP1 only when phosphorylated at Thr37 and/or Thr46, and may cross-react with 4E-BP2 and 4E-BP3 when phosphorylated at equivalent sites. Nonphospho-4E-BP1 (Thr46) (87D12) Rabbit mAb detects endogenous levels of 4E-BP1 only when dephosphorylated at Thr46. This antibody cross-reacts with 4E-BP2 and 4E-BP3 dephosphorylated at equivalent sites. Phospho-4E-BP1 (Ser65) Antibody detects endogenous levels of 4E-BP1 when phosphorylated at Ser65, and may also recognize 4E-BP1 when phosphorylated at Ser101. Phospho-4E-BP1 (Ser65) (174A9) Rabbit mAb detects endogenous levels of 4E-BP1 when phosphorylated at Ser65. Phospho-4E-BP1 (Thr70) Antibody detects endogenous levels of 4E-BP1 only when phosphorylated at Thr70. 4E-BP1 (53H11) Rabbit mAb detects endogenous levels of total 4E-BP1 protein. 4E-BP2 Antibody detects endogenous levels of total 4E-BP2 independent of phosphorylation and does not cross-react significantly with 4E-BP1.
Source / Purification
Monoclonal antibody is produced by immunizing animals with a synthetic phosphopeptide corresponding to residues surrounding Thr37 and Thr46 of mouse 4E-BP1, residues surrounding Thr46 of human 4E-BP1, or Ser112 of human 4E-BP1. Polyclonal antibodies are produced by immunizing animals with a synthetic peptide corresponding to the residues at the carboxy-terminus of human 4E-BP2 (#2845), or phosphopeptides surrounding mouse Ser65 (#9451) and human Thr70 (#5078) 4E-BP1. Polyclonal antibodies were purified by protein A and peptide affinity chromatography.
Translation repressor protein 4E-BP1 (also known as PHAS-1) inhibits cap-dependent translation by binding to the translation initiation factor eIF4E. Hyperphosphorylation of 4E-BP1 disrupts this interaction and results in activation of cap-dependent translation (1). Both the PI3 kinase/Akt pathway and FRAP/mTOR kinase regulate 4E-BP1 activity (2,3). Multiple 4E-BP1 residues are phosphorylated in vivo (4). While phosphorylation by FRAP/mTOR at Thr37 and Thr46 does not prevent the binding of 4E-BP1 to eIF4E, it is thought to prime 4E-BP1 for subsequent phosphorylation at Ser65 and Thr70 (5).
4E-BP2 and 4E-BP3 share high sequence homology with 4E-BP1, including conservation of the major FRAP/mTOR-dependent phosphorylation sites. Preliminary data suggests that phosphorylation of 4E-BP2 is regulated in a similar manner to that of 4E-BP1, although phosphorylation of this protein has not been as extensively studied (6).