AP-1, a dimeric protein complex composed of Jun and Fos proteins, plays a key role in the control of cell death, proliferation and transformation. Ap1 protein can be activated by many stimuli, including TPA, serum, growth factors and oncoproteins, TNF and IL-1, as well as by a variety of environmental stresses, such as UV radiation. When it is activated, AP1 protein binds to AP- DNA recognition element within the promoter regions of target genes and regulates the gene expression. Signosis has developed AP1 filter assay for monitoring DNA binding activity of AP1, which can be used for analyzing multiple samples simultaneously.