Evolution of antibody class switching: identification and transcriptional control of an Inu exon in the duck (Anas platyrhynchos).
Immunoglobulin class switching is characteristic to the tetrapod lineage, but the nature of this process has been elucidated only in mammals, where I-exon transcription initiates and directs the recombination in the IgH locus. Here, it is shown that an I-exon occurs 5' of the nu (IgY constant region) gene of the duck (Anas platyrhynchos): it is longer than mammalian I-exons and comprised primarily of tandem repeats. The Inu promoter was identified and shown to be responsive to stimulation with IL-4 but not LPS. It contains Oct, LYF-1, ATF, and C/EBP motifs. Site directed mutagenesis indicates that 2 C/EBP motifs are uniquely necessary for the response of the promoter to IL-4, as tested in the mouse pre-B cell line, 70Z/3. These results support the conclusion that the signal transduction pathways controlling I-exon promoter responses to cytokines have been highly conserved in vertebrate evolution.
Marine Biomedicine and Environmental Sciences Center and Department of Biochemistry and Molecular Biology, Medical University of South Carolina, 331 Fort Johnson Road, Charleston, SC 29412, USA. lundquml@musc.edu
Mats L
ML
Lundqvist
Bryan R
BR
McElveen
Darlene L
DL
Middleton
Robert
R
Chapman
Gregory W
GW
Warr
D000595:Amino Acid Sequence; D000818:Animals; D016207:Cytokines / Q000276:immunology; D004372:Ducks / Q000235:genetics / Q000276:immunology*; D005091:Exons / Q000235:genetics*; D015723:Gene Library; D005803:Genes, Immunoglobulin / Q000235:genetics*; D017578:Immunoglobulin Class Switching / Q000235:genetics*; D007127:Immunoglobulin Constant Regions / Q000235:genetics; D007136:Immunoglobulins / Q000235:genetics; D051379:Mice; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D011401:Promoter Regions, Genetic / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000276:immunology; D014158:Transcription, Genetic; D014162:Transfection
D016207:Cytokines; C016512:IgY; D007127:Immunoglobulin Constant Regions; D007136:Immunoglobulins