We have continued our studies of the mechanisms which regulate the activation, proliferation and differentiation of human B lymphocytes on both a cellular and a molecular level. We have mapped the CD22 gene transcription start sites and begun to characterize the expression of this gene at a molecular level. We have provided evidence that CD22 interacts with a broadly expressed ligand and begun to study the mechanisms by which CD22 signals. We have discovered a new B cell activation gene, BL34, that encodes for a protein which is a member of the basic HLH family and may function as a transcription factor. Recombinant BL34 protein has been made and new anti-BL34 antibodies produced. The gene for BL34 has been partially delineated and its chromosomal location identified. The human BL11 gene has been transfected into several lymphoid cell lines and a fusion protein between BL11 and the constant region of IgG has been made for functional studies. The distal portion of the CD20 promoter has been studied and found to contain a BSAP binding site, a NF-Y binding site, and a third unidentified site. Evidence for other regulatory regions in the CD20 gene have been found. Cis-elements in the proximal portion of the CD19 promoter has been found to be very active in lymphocytes. B cell lines deficient in CD19 have been established and will be very useful for studying B cell specific gene regulation. The GC kinase gene which is differentially expressed between mantle zone and germinal center B cells has been studied in further detail. Antibodies have been made and recombinant GC kinase produced in bacteria. Preliminary evidence for kinase activity has been found. The human homeobox gene HLX has been used to generate transgenic mice using the T cell receptor promoter/enhancer and the beta-actin promoter. These mice will be useful in understanding the functional consequences of HLX overexpression. A potential HLX target site has been identified as well as several potential target genes. Recombinant HLX protein has been in bacteria and is being used for functional studies and antibody production. Both the HLX gene and another human homeobox gene HB9 have been fully sequenced. Constructs for the expression HB9 have been made and transfected into various cell types. A study of one of the major transcriptional regulatory regions in the JC virus in the context of B cells has been completed. Methodology for studying differential gene expression in subsets of B cells have been established.
