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Immunohistochemical analysis of paraffin-embedded human breast carcinoma, using FosB (5G4) Rabbit mAb #2251 in the presence of control peptide (left) or FosB Blocking Peptide (right).

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Product Description

This peptide is used to block FosB (5G4) Rabbit mAb #2251 reactivity.


Quality Control

The quality of the peptide was evaluated by reversed-phase HPLC and by mass spectrometry. The peptide blocks FosB (5G4) Rabbit mAb #2251 by immunohistochemistry.

Product Usage Information

For immunohistochemistry, add twice the volume of peptide as volume of antibody used in 100 μl total volume. Incubate for a minimum of 30 minutes prior to adding the entire volume to the slide. Recommended antibody dilutions can be found on the relevant product data sheet.


Storage: Supplied in 20 mM potassium phosphate (pH 7.0), 50 mM NaCl, 0.1 mM EDTA, 1 mg/ml BSA and 5% glycerol. Store at –20°C.

The Fos family of nuclear oncogenes includes c-Fos, FosB, Fos-related antigen 1 (FRA1), and Fos-related antigen 2 (FRA2) (1). While most Fos proteins exist as a single isoform, the FosB protein exists as two isoforms: full-length FosB and a shorter form, FosB2 (Delta FosB), that lacks the carboxy-terminal 101 amino acids (1-3). The expression of Fos proteins is rapidly and transiently induced by a variety of extracellular stimuli including growth factors, cytokines, neurotransmitters, polypeptide hormones, and stress. Fos proteins dimerize with Jun proteins (c-Jun, JunB, and JunD) to form Activator Protein-1 (AP-1), a transcription factor that binds to TRE/AP-1 elements and activates transcription. Fos and Jun proteins contain the leucine-zipper motif that mediates dimerization and an adjacent basic domain that binds to DNA. The various Fos/Jun heterodimers differ in their ability to transactivate AP-1 dependent genes. In addition to increased expression, phosphorylation of Fos proteins by Erk kinases in response to extracellular stimuli may further increase transcriptional activity (4-6). Phosphorylation of c-Fos at Ser32 and Thr232 by Erk5 increases protein stability and nuclear localization (5). Phosphorylation of FRA1 at Ser252 and Ser265 by Erk1/2 increases protein stability and leads to overexpression of FRA1 in cancer cells (6). Following growth factor stimulation, expression of FosB and c-Fos in quiescent fibroblasts is immediate, but very short-lived, with protein levels dissipating after several hours (7). FRA1 and FRA2 expression persists longer, and appreciable levels can be detected in asynchronously growing cells (8). Deregulated expression of c-Fos, FosB, or FRA2 can result in neoplastic cellular transformation; however, Delta FosB lacks the ability to transform cells (2,3).


1.  Tulchinsky, E. (2000) Histol. Histopathol. 15, 921-928.

2.  Dobrzanski, P. et al. (1991) Mol. Cell. Biol. 11, 5470-5478.

3.  Nakabeppu, Y. and Nathans, D. (1991) Cell 64, 751-759.

4.  Rosenberger, S.F. et al. (1999) J. Biol. Chem. 274, 1124-1130.

5.  Sasaki, T. et al. (2006) Mol. Cell 24, 63-75.

6.  Basbous, J. et al. (2007) Mol. Cell. Biol. 27, 3936-3950.

7.  Kovary, K. and Bravo, R. (1991) Mol. Cell. Biol. 11, 2451-2459.

8.  Kovary, K. and Bravo, R. (1992) Mol. Cell. Biol. 12, 5015-5023.


Entrez-Gene Id 2354
Swiss-Prot Acc. P53539


For Research Use Only. Not For Use In Diagnostic Procedures.
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