fos基因家族由4個成員組成：fos、fosb、fosl1和fosl2。這些基因編碼亮氨酸拉鏈蛋白，可與Jun家族的蛋白質二聚，從而形成轉錄因子復合物AP-1。因此，fos蛋白被認為是細胞增殖、分化和轉化的調節因子。在某些情況下，fos基因的表達也與凋亡細胞死亡有關。
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. In some cases, expression of the FOS gene has also been associated with apoptotic cell death.