DNA-binding activity of Jun is increased through its interaction with Fos.
Transcription factor AP-1 mediates induction of a set of genes in response to the phorbol ester tumor promoter TPA. Recently, AP-1 preparations from HeLa cells were shown to contain a product of the c-JUN protooncogene (Jun/AP-1) which forms a tight complex with the Fos protein. In this paper, we examine the role of the Fos protein in the DNA-binding activity of the AP-1 complex. We show that the DNA-binding activity of bacterially expressed trpE-Jun fusion proteins is increased many-fold upon their interaction with Fos (or a Fos-related antigen) expressed from a baculovirus vector. The site of Fos interaction is within the DNA-binding domain of Jun/AP-1, and anti-Fos antibodies interfere with the binding of affinity purified AP-1 to DNA. These results suggest that, by associating with Jun/AP-1, Fos is responsible for the formation of a multimeric protein complex that has greater affinity for the target sequence than does Jun/AP-1 alone.
Allegretto
E A
EA
Department of Pharmacology, School of Medicine, University of California, San Diego, La Jolla 92093.
Smeal
T
T
Angel
P
P
Spiegelman
B M
BM
Karin
M
M
D004247:DNA / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism*; D005822:Genetic Vectors; D006367:HeLa Cells; D006801:Humans; D011518:Proto-Oncogene Proteins / Q000276:immunology / Q000378:metabolism*; D016760:Proto-Oncogene Proteins c-fos; D016755:Proto-Oncogene Proteins c-jun; D011519:Proto-Oncogenes; D014157:Transcription Factors / Q000378:metabolism*; D014162:Transfection
D004268:DNA-Binding Proteins; D011518:Proto-Oncogene Proteins; D016760:Proto-Oncogene Proteins c-fos; D016755:Proto-Oncogene Proteins c-jun; D014157:Transcription Factors; D004247:DNA