The jun and fos Gene Products

The oncogene of the FBJ murine osteosarcoma virus (fos) codes for a related nuclear protein that participates in transcriptional regulation. In human fibroblasts the fos protein is mostly associated with c-jun. The fos-jun complex binds specifically to DNA. Since fos alone does not show specific DNA binding, it is believed that jun is responsible for this affinity. Although jun can form homodimers that bind to DNA, the heterodimers formed between fos and jun show a greater affinity. The heterodimers are also more effective in transcription activation therefore the heterodimer is probably the functionally relevant state of the jun and fos proteins. 

Structural analysis indicates that the fos and jun proteins belong to a class of DNA-binding proteins that share the conserved structural motif known as the leucine zipper (see fig. 31.21). Thus, the dimerization of these two proteins is mediated by hydrophobic interaction between the leucine side chains of two leucine zipper domains. 

The jun-fos protein complex interacts with regulatory regions of numerous genes. We have yet to find out which of these target genes are involved in aberrant cellular growth. 

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The myc Gene Product The jun and fos Gene Products The Transition from Protooncogene to Oncogene Carcinogenesis Is a Multistep Process... 

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