The activator protein 1 (AP-1) transcription factor is a dimeric complex that comprises members of the JUN, FOS, ATF and MAF protein families with FOS and JUN being the most common proteins in mammalian cells. AP-1 activity is induced by growth factors, cytokines and oncoproteins. Upon activation, AP-1 binds to the TPA Responsive element (TRE) and induces transcription of a variety of genes involved in multiple cellular functions such as proliferation, survival, differentiation and transformation.
Cells will undergo genotypic changes resulting in reduced responsiveness over time in normal cell culture conditions. Genetic instability is a biological phenomenon that occurs in all stably transfected cells. Therefore, it is critical to prepare an adequate number of frozen stocks at early passages.