Cloning and expression of AP-2, a cell-type-specific transcription factor that activates inducible enhancer elements.

Human AP-2 is a sequence-specific DNA-binding protein that interacts with inducible viral and cellular enhancer elements to stimulate transcription of selected genes. Here, we report the isolation and characterization of a human cDNA clone containing the entire protein-coding region of AP-2. The deduced primary amino acid sequence of AP-2 does not contain a domain resembling any previously identified DNA binding motif. However, an interesting feature of the AP-2 protein is a clustered arrangement of proline and glutamine residues that have been found recently within the activation domains of other transcription factors. Expression of the AP-2 clone in bacteria yields a protein that binds to DNA and activates transcription in vitro in a comparable manner to native human AP-2. Transfection of cDNA clones into Drosophila cells indicates that the AP-2 gene product can also activate gene expression in vivo in a DNA template-dependent manner. Expression of endogenous AP-2 is repressed in a hepatoma cell line and stimulated following retinoic-acid-induced differentiation of a human teratocarcinoma cell line. This indicates that AP-2 may be a transcription factor involved in the control of developmentally regulated gene expression.