Fig. 3. Functions of AP-1 subunits in various cellular processes and disease. Antagonistic (indicated by the double-headed arrow) or common tasks for AP-1 members are observed in various cell types. Positive, negative or even dual functions of individual subunits influence pivotal cellular processes, such as differentiation, cell-cycle regulation or apoptosis. Deregulation of these processes by alterations in either single or multiple AP-1 subunits, thereby modulating AP-1 net activity, can be fatal for the cell and organism.