Enhancer and promoter activity in the JH to IGHM intron of the Pekin duck, Anas platyrhynchos.
A transcriptional enhancer, Emu, was defined in the IGH locus of the Pekin duck, Anas platyrhynchos. Regions of DNA from the JH to IGHM intron were cloned into reporter constructs containing the SV40 promoter and transiently transfected into chicken B and T lymphocytes. A strong transcriptional activity, of several hundred-fold greater than that of a reporter construct with the promoter alone, was localized to a 281bp region that contains 2 E-box motifs, CAGCTG. This fragment showed enhancer activity in both orientations and was active in chicken B cells but not in T cells. When the activity of the enhancer was tested in constructs without a promoter, it showed high transcriptional activity in the forward orientation, but much less activity (by two orders of magnitude) when tested in the reverse orientation. This suggests that the fragment contains not only enhancer activity but may contain promoter activity analogous to that of the Imu promoter described in mammals. Thus it appears that the location, but not the fine structure, of the Emu enhancer was established before the evolutionary divergence of the avian and mammalian lineages some 300Myr ago.
Lundqvist
Mats L
ML
Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, SC 29425, USA.
McElveen
Bryan R
BR
Middleton
Darlene L
DL
Warr
Gregory W
GW
D000818:Animals; D002461:Cell Line, Transformed; D002645:Chickens; D004372:Ducks / Q000235:genetics* / Q000276:immunology*; D004742:Enhancer Elements, Genetic / Q000235:genetics*; D050438:Genes, Immunoglobulin Heavy Chain / Q000235:genetics*; D017578:Immunoglobulin Class Switching / Q000235:genetics*; D007438:Introns / Q000235:genetics*; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic / Q000235:genetics*