Mouse Monoclonal Antibody to c-FOS (cFos, Fos, AP-1) Cat# MCA-1B62

      The FOS gene and protein were originally identified as the transforming element in a viral oncogene. The transforming protein was named v-FOS, for viral FOS, and the normal cellular non-transforming proto-oncogene was called c-FOS, for cellular FOS. The c-Fos protein is also known as cFOS, AP-1, C-p55, Fos proto-oncogene and AP-1 transcription factor subunit. FOS is an acronym for "FBJ murine osteogenic sarcoma", the virus in which the gene product was first discovered. The c-FOS protein is a normal gene acting as an on/off switch controlling the expression of many other genes. The v-FOS form is mutated to stay in the on position, this persistently activating other genes and promoting unregulated cell division. The unmutated c-FOS is an "immediate-early" gene, so-called because protein expression is usually very low but increases rapidly and transiently in response to a wide array of stimuli including serum, growth factors, tumor promoters, cytokines, and UV radiation. Newly expressed c-FOS protein associates with JUN family and other basic leucine-zipper (bZIP) proteins to create a variety of activator protein-1 (AP-1) complexes (1). AP-1 complexes specifically activate the expression of many other genes and so regulate cellular responses to stimuli which may result in cell proliferation, differentiation, neoplastic transformation, apoptosis, and response to stress (2). The regulated expression of c-FOS therefore plays an important role in many cellular functions. Site specific phosphorylation activates c-FOS, while sumoylation of c-FOS inhibits the AP-1 transcriptional activity (3,4). Since c-FOS expression is induced in neurons which are rapidly firing action potentials, appropriate c-Fos antibodies can be used to identify activated neurons in tissues for tracing neuronal projections and other purposes (5). Using current techniques it is possible to identify such activated cells using c-FOS staining then obtain further data on their specific protein and mRNA expression.

Section of adult rat hippocampus processed for formalin fixed paraffin embedded IHC and probed with 1:2,000 dilution of MCA-1B62 detected with DAB (brown) using the Vector Labs ImmPRESS method and reagents with citra buffer retrieval. The antibody strongly recognizes the nuclei of a few spontaneously activated neurons against a background of apparently unreactive cells. Mouse select image for larger view.

1. Mildle-Langosch K. The Fos family of transcription factors and their role in tumourigenesis. Eur. J. Cancer 41:2449-2461 (2005).
2. Chiu R, et al. The c-Fos protein interacts with c-Jun/AP-1 to stimulate transcription of AP-1 responsive genes. Cell 54:541–52 (1988).
3. Karin M. The regulation of AP-1 activity by mitogen activated protein kinases. J Biol Chem. 270:16483-6 (1995).
4. Bossis G, et al. Down-regulation of c-Fos/c-Jun AP-1 dimer activity by sumoylation. Mol Cell Biol.25(16):6964-79 (2005).
5. Dragunow M, Faull R. The use of c-fos as a metabolic marker in neuronal pathway tracing. J. Neurosci. Mets. 29:261–265 (1989).