Jun-B differs in its biological properties from, and is a negative regulator of, c-Jun.
c-Jun, Jun-B, and Jun-D proteins bind to the TPA response element (TRE) either as homodimers or as Jun-Fos heterodimers. We demonstrate that c-Jun and Jun-B nevertheless differ markedly in their ability to activate AP-1 responsive genes. c-Jun is an efficient activator of the c-jun and collagenase promoters, which contain a single TRE; Jun-B is not. Furthermore, Jun-B inhibits activation of these promoters by c-Jun. On the other hand, like c-Jun, Jun-B is an efficient activator of constructs containing multimeric TREs. Using chimeric proteins, we show that the distinct behavior of c-Jun and Jun-B is due to differences in their activation domains. Trans-activation by Jun-B depends on cooperative interactions between adjacently bound factors, while activation by c-Jun does not require such interactions. This differential behavior greatly expands the regulatory potential of the Jun family.
Chiu
R
R
Department of Pharmacology, School of Medicine, University of California, San Diego, La Jolla 92093.
Angel
P
P
Karin
M
M
D000818:Animals; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000378:metabolism*; D015870:Gene Expression; D015972:Gene Expression Regulation, Neoplastic; D006367:HeLa Cells / Q000378:metabolism; D006706:Homeostasis; D006801:Humans; D007700:Kinetics; D051379:Mice; D009857:Oncogenes; D010957:Plasmids; D011494:Protein Kinases / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D016755:Proto-Oncogene Proteins c-jun; D011519:Proto-Oncogenes; D014157:Transcription Factors / Q000378:metabolism*; D014162:Transfection
D004268:DNA-Binding Proteins; D011518:Proto-Oncogene Proteins; D016755:Proto-Oncogene Proteins c-jun; D014157:Transcription Factors; D011494:Protein Kinases