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In the fields of molecular biology and genetics, c-Fos is a proto-oncogene that is the human homolog of the retroviral oncogene v-fos.〔Curran, T: The c-fos proto-oncogene. In: Reddy EP, Skalka AM, Curran T (eds.). The Oncogene Handbook 1988 Elsevier, New York, pp 307–327,〕 It was first discovered in rat fibroblasts as the transforming gene of the FBJ MSV (Finkel–Biskis–Jinkins murine osteogenic sarcoma virus). It is a part of a bigger Fos family of transcription factors which includes c-Fos, FosB, Fra-1 and Fra-2 as well as smaller FosB splice variants, FosB2 and ΔFosB. 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. It plays an important role in many cellular functions and has been found to be overexpressed in a variety of cancers. == Structure and function == c-fos is a 380 amino acid protein with a basic leucine zipper region for dimerisation and DNA-binding and a transactivation domain at C-terminus. Unlike Jun proteins, it cannot form homodimers, only heterodimers with c-jun. ''In vitro'' studies have shown that Jun–Fos heterodimers are more stable and have stronger DNA-binding activity than Jun–Jun homodimers. A variety of stimuli, including serum, growth factors, tumor promoters, cytokines, and UV radiation induce their expression. The c-fos mRNA and protein is generally among the first to be expressed and hence referred to as an immediate early gene. It is rapidly and transiently induced, within 15 minutes of stimulation. Its activity is also regulated by posttranslational modification caused by phosphorylation by different kinases, like MAPK, cdc2, PKA or PKC which influence protein stability, DNA-binding activity and the trans-activating potential of the transcription factors. It can cause gene repression as well as gene activation, although different domains are believed to be involved in both processes. It is involved in important cellular events, including cell proliferation, differentiation and survival; genes associated with hypoxia; and angiogenesis; which makes its dysregulation an important factor for cancer development. It can also induce a loss of cell polarity and epithelial-mesenchymal transition, leading to invasive and metastatic growth in mammary epithelial cells. The importance of c-fos in biological context has been determined by eliminating endogenous function by using anti-sense mRNA, anti-c-fos antibodies, a ribozyme that cleaves c-fos mRNA or a dominant negative mutant of c-fos. The transgenic mice thus generated are viable, demonstrating that there are c-fos dependent and independent pathways of cell proliferation, but display a range of tissue-specific developmental defects, including osteoporosis, delayed gametogenesis, lymphopenia and behavioral abnormalities. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「C-Fos」の詳細全文を読む スポンサード リンク
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