Transactivation of mouse insulin-like growth factor II (IGF-II) gene promoters by the AP-1 complex

The mouse insulin-like growth factor II gene (Igf2) is transcribed from three promoters (P1, P2 and P3), and is expressed in a tissue-specific and developmentally regulated fashion; however, little information is available on the transcription factors controlling Igf2 expression. The AP-1 complex is a transcription factor involved in the regulation of a variety of genes, including those encoding certain growth factors. We show that Igf2 P3 is transactivated by AP-1 in a transient expression assay, and that this effect is mediated through two non-consensus AP-1 binding sites characterised by DNA-protein interaction studies. Mutational analysis indicates these sites are required for AP-1 responsiveness and full promoter activity.