Promoter-specific trans-activation and inhibition mediated by JunB.
Nuclear levels of c-Jun, JunB, c-Fos, and LRF-1 (liver regeneration factor) are high for a large fraction of the G1 phase in regenerating liver and mitogen-stimulated hepatic cells. Previously, JunB was regarded as a less potent transcriptional activator than c-Jun that could also function as a repressor. However, we found that, like c-Jun, JunB alone or LRF-1/JunB strongly transactivates a cAMP-responsive promoter. Unlike c-Jun, JunB represses several AP-1 or activator of transcription factor site-containing promoters, and this inhibition is greatly enhanced in the presence of LRF-1. Here, we identify separate regions of JunB required for trans-activation and repression of these promoters. Deletion analysis shows that the region involved in trans-activation function is highly conserved among all Jun family members and corresponds to activator domain (A1) of c-Jun. In contrast, repression is maximal in the presence of both the DNA-binding domain and a region proximal to the basic region that is highly divergent among Jun proteins. Functional distinctions between Jun proteins during induction of the growth response and tumorigenesis may be accounted for by promoter-specific activation and repression mediated by regional differences in Jun family proteins.
Hsu
J C
JC
Department of Genetics, University of Pennsylvania School of Medicine, Philadelphia 19104-6145.
Cressman
D E
DE
Taub
R
R
D016475:3T3 Cells; D051700:Activating Transcription Factor 3; D000818:Animals; D001483:Base Sequence; D004268:DNA-Binding Proteins / Q000235:genetics / Q000502:physiology*; D017353:Gene Deletion; D016758:Genes, jun; D051379:Mice; D008969:Molecular Sequence Data; D009154:Mutation; D016133:Polymerase Chain Reaction; D011401:Promoter Regions, Genetic; D016755:Proto-Oncogene Proteins c-jun / Q000235:genetics / Q000502:physiology*; D012333:RNA, Messenger; D014162:Transfection
D051700:Activating Transcription Factor 3; D004268:DNA-Binding Proteins; D016755:Proto-Oncogene Proteins c-jun; D012333:RNA, Messenger; C068616:liver regeneration factor 1