Octamer independent activation of transcription from the kappa immunoglobulin germline promoter.
Previous analyses of immunoglobulin V region promoters has led to the discovery of a common octamer motif which is functionally important in the tissue-specific and developmentally regulated transcriptional activation of immunoglobulin genes. The germline promoters (Ko) located upstream of the J region gene segments of the kappa locus also contain an octamer motif (containing a single base pair mutation and referred to as the variant octamer) which has been shown previously to bind Oct-1 and Oct-2 transcription factors in vitro. To further elucidate the role of this variant octamer motif in the regulation of germline transcription from the unrearranged kappa locus, we have quantitated the relative binding affinity of Oct-1 and Oct-2 for the variant octamer motif and determined the functional role of this octamer motif in transcriptional activation. We find that, although the variant octamer motif binds Oct-1 and Oct-2 in vitro with 5-fold lower affinity than the consensus octamer motif, mutation of the variant octamer motif to either a consensus octamer or non-octamer motif has no effect on transcriptional activation from the germline promoter. We also find significant differences in activation of germline and V region promoters by kappa enhancers. Our results suggest that the germline promoters and V region promoters differ in their dependence on octamer for activation and respond differently to enhancer activation. These findings have important implications in regulation of germline transcription as well as concomitant activation of the V-J recombination of the kappa light chain locus.
Prabhu
A
A
Institute of Human Genetics, University of Minnesota, Minneapolis 55455, USA.
O'Brien
D P
DP
Weisner
G L
GL
Fulton
R
R
Van Ness
B
B
D000818:Animals; D001402:B-Lymphocytes; D001483:Base Sequence; D001665:Binding Sites; D004247:DNA / Q000737:chemistry / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism*; D005822:Genetic Vectors; D018398:Homeodomain Proteins / Q000378:metabolism*; D051863:Host Cell Factor C1; D006801:Humans; D007145:Immunoglobulin kappa-Chains / Q000235:genetics*; D051379:Mice; D009101:Multiple Myeloma; D016296:Mutagenesis; D050811:Octamer Transcription Factor-1; D050813:Octamer Transcription Factor-2; D016133:Polymerase Chain Reaction; D011401:Promoter Regions, Genetic; D014157:Transcription Factors / Q000378:metabolism*; D014158:Transcription, Genetic; D014162:Transfection; D014407:Tumor Cells, Cultured
D004268:DNA-Binding Proteins; C497692:HCFC1 protein, human; C497693:Hcfc1 protein, mouse; D018398:Homeodomain Proteins; D051863:Host Cell Factor C1; D007145:Immunoglobulin kappa-Chains; D050811:Octamer Transcription Factor-1; D050813:Octamer Transcription Factor-2; C494165:POU2F1 protein, human; C058435:POU2F2 protein, human; C494166:Pou2f1 protein, mouse; C489206:Pou2f2 protein, mouse; D014157:Transcription Factors; D004247:DNA