Regulation of antibody class switching to IgE: characterization of an IL-4-responsive region in the immunoglobulin heavy-chain germline epsilon promoter.
A large body of data indicate that antibody class switching is directed by cytokines by inducing or repressing transcription from unrearranged, or germline, CH genes. IL-4 induces transcription of the germline C epsilon genes in activated B cells, and subsequently cells in this population will undergo switch recombination to IgE. Furthermore, the data suggest that transcription of germline C epsilon genes is required for class switching. In this paper we define DNA elements required for induction of transcription of the germline C epsilon genes by IL-4. To do this, segments of DNA from the 5' flank of the initiation sites for germline epsilon RNA were ligated to a luciferase reporter gene and transfected into two mouse B-cell lines, one of which can be induced to switch to IgE. By analysis of a series of 5' deletion constructs and linker-scanning mutations, we demonstrate that a 46-bp segment (residing at -126/-79 relative to the first RNA initiation site) contains an IL-4 responsive region. This segment binds three transcription factors: the recently described NF-IL4, one or more members of the C/EBP family of transcription factors, and NF-kappa B/p50. Mutation of any of the binding sites for these three factors abolishes or reduces IL-4 inducibility of the epsilon promoter. A 27-bp segment within this IL-4 response region containing binding sites for NF-IL4 and a C/EBP factor is sufficient to transfer IL-4 inducibility to a minimal c-fos promoter.
D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D004268:DNA-Binding Proteins / Q000378:metabolism; D005786:Gene Expression Regulation; D005803:Genes, Immunoglobulin / Q000187:drug effects; D017930:Genes, Reporter; D006801:Humans; D017578:Immunoglobulin Class Switching / Q000187:drug effects; D007127:Immunoglobulin Constant Regions / Q000235:genetics*; D007073:Immunoglobulin E / Q000235:genetics*; D007143:Immunoglobulin Heavy Chains / Q000235:genetics*; D015847:Interleukin-4 / Q000494:pharmacology / Q000502:physiology*; D008156:Luciferases / Q000096:biosynthesis; D051379:Mice; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D011401:Promoter Regions, Genetic / Q000187:drug effects; D016415:Sequence Alignment; D012689:Sequence Homology, Nucleic Acid; D014157:Transcription Factors / Q000378:metabolism
D004268:DNA-Binding Proteins; D007127:Immunoglobulin Constant Regions; D007143:Immunoglobulin Heavy Chains; D014157:Transcription Factors; D015847:Interleukin-4; D007073:Immunoglobulin E; D008156:Luciferases