FBJ murine osteosarcoma viral oncogene homolog B also known as FOSB (in humans) or FosB (in other species) is a protein that, in humans, is encoded by the FOSB gene.
The Fos gene family consists of 4 members: FOS, FOSB, FOSL1, and FOSL2. These genes encode leucine zipper proteins that can dimerize with proteins of the JUN family, thereby forming the transcription factor complex AP-1. As such, the FOS proteins have been implicated as regulators of cell proliferation, differentiation, and transformation.
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