 It is a part of a bigger Fos family of transcription factors which includes c-Fos, FosB, Fra-1 and Fra-2.It has been mapped to chromosome region 14q21→q31.c-Fos encodes a 62 kDa protein, which forms heterodimer with c-jun (part of Jun family of transcription factors), resulting in the formation of AP-1 (Activator Protein-1) complex which binds DNA at AP-1 specific sites at the promoter and enhancer regions of target genes and converts extracellular signals into changes of gene expression.