The ability to synthesize immunoglobulins is a unique and characteristic property of cells in the B lymphocyte lineage. At least two discrete segments of an immunoglobulin kappa gene are essential for its expression in B lymphoid cells. One of these, the intronic control region (ICR), is closely linked to the kappa constant coding locus, and functions as a transcriptional enhancer. The second is a highly conserved octanucleotide sequence (ATTTGCAT) situated within the kappa promoter region; the mechanism by which it affects gene expression is unknown. Our goal is to elucidate the function of this octanucleotide block, and to determine how these two distinct genetic elements interact, with each other and with tissue-specific cellular factors, to control kappa gene transcription. This information is likely to be of great value in understanding how the activity of specific eukaryotic genes is regulated. Just as importantly, our studies of immunoglobulin gene regulation could reveal tissue-specific aspects of the transcriptional apparatus of B lymphoid cells, which could ultimately be exploited in designing novel treatment modalities directed against B cell malignancies. Using techniques of recombinant DNA, we will evaluate the transcriptional function of modified kappa genes introduced into lymphoid and non-lymphoid cells in a transient expression assay. This assay will be used to determine whether the kappa promoter is preferentially susceptible to the action of the ICR as compared to other types of enhancer elements, and, conversely, whether the ICR acts selectively upon the kappa promoter. The role of the octanucleotide block in this interaction will be evaluated, and we will seek evidence of tissue-specific factors influencing kappa promoter function through mechanisms independent of the ICR enhancer. We also plan to alter systematically the sequence and location of the octanucleotide element, and to determine the effects of these mutations on kappa promoter function. In addition, we will seek direct evidence of tissue-specific factors binding to the octanucleotide block in vivo and in vitro, and will investigate the role of these factors in producing the B cell phenotype.
