We have continued our studies of the mechanism which regulate the activation, proliferation and differentiation of human B lymphocytes on both a cellular and a molecular level. We have isolated the B cell specific CD22 gene, and characterized its structure, transcriptional start sites, and begun to study the regulation of its expression. We have fully sequenced two novel cDNA clones, BL11 and BL34, which were found to be induced in high levels in activated B cells. Studies are in progress to characterize the genomic structures of these two genes, to generate antibodies against the BL11 and BL34 proteins, and to express these proteins in bacteria and mammalian cells. The proximal portion of the CD20 promoter has been studied and found to contain a diverged Oct-2 binding site which is important in the B cell specific expression of CD20 in mature B cells and the induction of CD20 expression in a pre-B cell line. Mobility shift assays have identified other potentially interesting DNA binding proteins in the more distal CD20 promoter. In vivo foot printing has been established in the laboratory and is being used to characterize the CD20 promoter and will be used to help the analysis of the CD19 and CD22 promoters as well. Analysis of the CD19 promoter is in progress and several B cell lines which are CD19 negative have been established. A cDNA predicted to encode for a novel protein kinase, GCK, which is differentially expressed at the mRNA level, expressed in germinal center but not mantle zone B cells, has been isolated. The human homeobox gene HB24 has been used to generate transgenic mice using the T cell receptor promoter/enhancer. The HB24 transgenic mice have a major defect in CD4+ T cell development and the thymuses of these mice fail to undergo normal thymic involution. Both HB24 and HB9 , another human homeobox gene, were found to be expressed at high levels in acute leukemic, but not in chronic leukemic cells. Injection of nude mice with Jurkat cells transfected with HB24 induces tumors while control cells do not. Genomic clones for HB9 and HB24 have been isolated and have been partially characterized. The HB9 and HB24 genes have been co-localized to the long area of chromosome 1.
