HS1,2 enhancer regulation of germline epsilon and gamma2b promoters in murine B lymphocytes: evidence for specific promoter-enhancer interactions.
During an immune response, activated B cells develop into high rate Ig-secreting plasma cells. They also switch from production of IgM to IgG, IgA, or IgE. This process requires a DNA recombination event, which is regulated at the transcriptional level by the production of isotype-specific, sterile germline (GL) transcripts. Induction of these transcripts is controlled by GL promoters and, possibly, by IgH 3' enhancers. We investigated the interaction of the GL epsilon and gamma2b promoters with the HS1,2 enhancer using transiently transfected mouse primary B cells and cell lines. The constructs used for the transfections contained a GL promoter upstream and HS1,2 downstream of a luciferase reporter gene. Both GL epsilon and gamma2b promoters synergized strongly with the HS1,2 enhancer in activated primary B cells, a mature B cell line, and a plasma cell line. We show that the major activity of HS1,2 in activated primary B cells occurs within a 310-bp fragment that includes NF-kappaB, OCT, and NF of activated B cells (Ets/AP-1) sites. By mutating the consensus sequences for various transcription factors, we have determined which sites in HS1,2 are important for synergy with the GL epsilon and gamma2b promoters. Our findings indicate that different sites in HS1,2 might selectively interact with the GL epsilon and gamma2b promoters. We also provide evidence that B cell-specific activator protein is not an absolute suppressor of HS1,2 activity.
Laurencikiene
J
J
Department of Cell and Molecular Biology, Karolinska Institutet, Stockholm, Sweden. Jurga.Laurencikiene@cmb.ki.se
Deveikaite
V
V
Severinson
E
E
D000818:Animals; D000917:Antibody Formation / Q000235:genetics*; D001402:B-Lymphocytes / Q000276:immunology*; D001665:Binding Sites; D016384:Consensus Sequence; D004268:DNA-Binding Proteins / Q000378:metabolism; D004742:Enhancer Elements, Genetic / Q000235:genetics*; D005786:Gene Expression Regulation / Q000235:genetics*; D005803:Genes, Immunoglobulin; D017930:Genes, Reporter; D051863:Host Cell Factor C1; D017578:Immunoglobulin Class Switching / Q000235:genetics*; D007143:Immunoglobulin Heavy Chains / Q000235:genetics*; D008156:Luciferases / Q000032:analysis / Q000235:genetics; D008213:Lymphocyte Activation; D051379:Mice; D008810:Mice, Inbred C57BL; D008808:Mice, Inbred CBA; D016328:NF-kappa B / Q000378:metabolism; D009687:Nuclear Proteins / Q000378:metabolism; D050811:Octamer Transcription Factor-1; D051757:PAX5 Transcription Factor; D011401:Promoter Regions, Genetic / Q000235:genetics*; D050783:Proto-Oncogene Proteins c-ets; D018808:Transcription Factor AP-1; D014157:Transcription Factors / Q000378:metabolism; D014158:Transcription, Genetic; D014162:Transfection
D004268:DNA-Binding Proteins; C497693:Hcfc1 protein, mouse; D051863:Host Cell Factor C1; D007143:Immunoglobulin Heavy Chains; D016328:NF-kappa B; C096031:NFAB complex; D009687:Nuclear Proteins; D050811:Octamer Transcription Factor-1; D051757:PAX5 Transcription Factor; C497282:Pax5 protein, mouse; C494166:Pou2f1 protein, mouse; D050783:Proto-Oncogene Proteins c-ets; D018808:Transcription Factor AP-1; D014157:Transcription Factors; D008156:Luciferases