Fos and Jun bind cooperatively to the AP-1 site: reconstitution in vitro.
The protein products of the fos (Fos) and jun (Jun) proto-oncogenes have been shown to associate with a DNA element known as the transcription factor activator protein-1 (AP-1) binding site. Jun (previously known as the Fos-binding protein p39) and Fos form a protein complex in the nucleus. To investigate the nature of the association of Fos and Jun with the AP-1 site, and to determine the role of protein complex formation in DNA-binding, we have reconstituted the protein-protein and protein-DNA interactions in vitro using Fos and Jun synthesized in reticulocyte lysates. The Fos-Jun complex formed extremely rapidly in vitro and possessed similar, though not identical, chromatographic and sedimentation properties to the complex isolated from cell extracts. Jun exhibited a low level of AP-1 binding activity; however, this was evident only at high concentrations of DNA. Fos did not bind to the AP-1 site on its own; however, it acted cooperatively with Jun to give enhanced DNA-binding activity. The increased affinity of the Fos-Jun complex for DNA resulted from a stabilization of the protein-DNA complex. These data demonstrate a cooperative interaction between the protein products of two proto-oncogenes with a DNA element involved in transcriptional regulation.
Rauscher
F J
FJ
Department of Molecular Oncology, Roche Institute of Molecular Biology, Roche Research Center, Nutley, New Jersey 07110.
Voulalas
P J
PJ
Franza
B R
BR
Curran
T
T
D000494:Allosteric Regulation; D000818:Animals; D001665:Binding Sites; D002499:Centrifugation, Density Gradient; D003001:Cloning, Molecular; D004247:DNA / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics*; D004591:Electrophoresis, Polyacrylamide Gel; D009841:Oligonucleotides / Q000235:genetics; D011499:Protein Processing, Post-Translational; D011518:Proto-Oncogene Proteins / Q000235:genetics*; D016760:Proto-Oncogene Proteins c-fos; D016755:Proto-Oncogene Proteins c-jun; D012313:RNA / Q000138:chemical synthesis; D014157:Transcription Factors / Q000235:genetics*
D004268:DNA-Binding Proteins; D009841:Oligonucleotides; D011518:Proto-Oncogene Proteins; D016760:Proto-Oncogene Proteins c-fos; D016755:Proto-Oncogene Proteins c-jun; D014157:Transcription Factors; D012313:RNA; D004247:DNA