Novel Jun- and Fos-related proteins in Drosophila are functionally homologous to enhancer factor AP-1

A homolog of mammalian enhancer binding factor AP-1 was detected in Drosophila and was purified from embryo nuclear extracts by sequence-specific DNA affinity chromatography. The purified fraction, dAP-1, displays the sequence specificity as well as transcriptional activation properties of mammalian AP-1 and consists of two major proteins of mol. wts 40 and 70 kd. Antibody cross-reactivity experiments suggest that these proteins are Drosophila homologs of proto-oncogene products, Jun and Fos. The Drosophila Jun- and Fos-related antigens, when separated, are individually capable of sequence-specific DNA binding, and the Jun-related antigen activates transcription in vitro.