title: The dorsal-related immunity factor, Dif, is a sequence-specific trans-activator of Drosophila Cecropin gene expression.
abstract: A new member of the Rel family of transcription factors, the dorsal-related immunity factor, Dif, was recently cloned and suggested to be involved in regulating the immune response in Drosophila. Despite its classification as a Rel family member, the Dif cDNA-encoded product has not been proven previously to be a transcription factor. We now present evidence that the Dif gene product trans-activates the Drosophila Cecropin A1 gene in co-transfection assays. The transactivation requires a 40 bp upstream element including an insect kappa B-like motif. A dimer of the kappa B-like motif 5'-GGGGATTTTT inserted into a minimal promoter conferred high levels of reporter gene expression by Dif, while a multimer of several mutated versions of this motif was not activated, demonstrating the sequence specificity of Dif. Full trans-activation by Dif requires the C-terminal part of the protein. The morphogen dorsal (dl) can also activate the Cecropin A1 promoter, but to a lesser extent and in a less sequence-specific manner than Dif. Simultaneous overexpression of Dif and dl in co-transfection assays revealed that dl possesses a dominant negative effect on Dif transactivation. This study establishes that Dif is a sequence-specific transcription factor and is probably a key activator of the immune response in Drosophila.
authors.affiliation: Department of Molecular Biology, Arrhenius Laboratories for Natural Sciences, Stockholm University, Sweden.
authors.forename: U M
authors.initials: UM
authors.lastname: Petersen
authors.forename: G
authors.initials: G
authors.lastname: Björklund
authors.forename: Y T
authors.initials: YT
authors.lastname: Ip
authors.forename: Y
authors.initials: Y
authors.lastname: Engström
mesh_terms: D000818:Animals; D001483:Base Sequence; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000096:biosynthesis / Q000235:genetics*; D004330:Drosophila / Q000235:genetics* / Q000378:metabolism; D029721:Drosophila Proteins; D005246:Feedback; D017344:Genes, Insect / Q000235:genetics*; D017930:Genes, Reporter; D006434:Hemocytes / Q000378:metabolism; D007301:Insect Hormones / Q000096:biosynthesis / Q000235:genetics*; D007814:Larva / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation; D009687:Nuclear Proteins / Q000096:biosynthesis / Q000235:genetics; D010750:Phosphoproteins / Q000096:biosynthesis / Q000235:genetics; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000096:biosynthesis; D014157:Transcription Factors; D015533:Transcriptional Activation; D014162:Transfection
chemical_list: D004268:DNA-Binding Proteins; C084428:Dif protein, Drosophila; D029721:Drosophila Proteins; D007301:Insect Hormones; D009687:Nuclear Proteins; D010750:Phosphoproteins; D012333:RNA, Messenger; D014157:Transcription Factors; C062236:dl protein, Drosophila