The c-fos protein, also known as FBJ murine viral (v-fos) oncogene homolog , is a 62 kD cellular oncogene. The c-fos protein contains a bZIP region with a DNA-binding domain and a leucine zipper domain. Together with c-jun, c-jun proteins form the heterodimeric AP-1 complex that binds to the TRE elements of cellular and viral genes including collagenase, interleukin 2, stromelysin, SV40 and polyoma among others. c-fos is expressed in a variety of normal adult tissues and has been implicated as a critical transcription factor for skeletal formation and maintenance. This transcription factor is modified by phosphorylation by a number of upstream kinases and has been shown to interact with a variety of other proteins involved in transcriptional regulation. c-fos has been implicated in the development of fibrous bone dysplasia and osteosarcoma. The c-fos protein has been shown to interact with a variety of other proteins including c-jun, TFIID, NCOA2, NFAT1, CHOP, ELK1, SRC1, and ETS1. The Poly6244 antibody recognizes human, rat, and mouse c-fos and has been shown to be useful for Western blotting, immunoprecipitation, and immunohistochemistry.