The C/EBP family of transcriptional activators is functionally important for Ig VH promoter activity in vivo and in vitro.
We have examined the functional importance of binding sites for C/EBP family members (E sites), in two Ig VH promoters: VH1, a member of the S107 family, and BCL1, a member of the J558 family. Mutation of the E site in the VH1 promoter diminishes transcription in vivo to 59% of wild-type and transcription from the BCL1 promoter in vitro is inhibited to an average of 39% of wild-type by competition with E site oligonucleotides. Purified E site binding proteins from plasmacytoma cells stimulated BCL1 transcription in vitro 2.3-fold. Although five C/EBP family proteins are known which bind the E site, antibody ablation of DNA:protein complexes resolved by electrophoretic mobility shift assays showed that Ig/EBP-1 is the only E site binding protein detectable in early B cell lines; more mature B cells contain Ig/EBP-1 and NF-IL6. We also show by antibody-depletion that Ig/EBP-1 activates the BCL1 promoter in vitro.
Cooper
C
C
Department of Microbiology, Columbia University College of Physicians and Surgeons, New York, NY 10032.
Johnson
D
D
Roman
C
C
Avitahl
N
N
Tucker
P
P
Calame
K
K
D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D022762:CCAAT-Enhancer-Binding Proteins; D004268:DNA-Binding Proteins / Q000502:physiology; D005803:Genes, Immunoglobulin; D007143:Immunoglobulin Heavy Chains / Q000235:genetics*; D007135:Immunoglobulin Variable Region / Q000235:genetics*; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000502:physiology; D011401:Promoter Regions, Genetic; D011817:Rabbits; D015534:Trans-Activators / Q000502:physiology*
D022762:CCAAT-Enhancer-Binding Proteins; D004268:DNA-Binding Proteins; D007143:Immunoglobulin Heavy Chains; D007135:Immunoglobulin Variable Region; D009687:Nuclear Proteins; D015534:Trans-Activators