A NOVEL GENE-PRODUCT ASSOCIATED WITH MU-CHAINS IN IMMATURE B-CELLS

A previously unreported B cell specific gene, which we have named 8HS- 20, was isolated from the cDNA library of a pre-B cell clone by subtra ction and differential hybridization. This gene is selectively express ed as a 0.75 kb transcript in pre-B and bone marrow-derived B cell lin es; a transcript of the same size is also found in bone marrow and, al beit at low levels, in spleen. The deduced amino acid sequence of the 8HS-20 cDNA displayed homology to a B cell specific gene, VpreB-1, and to members of the immunoglobulin supergene family including Vlambda, Vchi, V(H), TCRValpha, Vbeta and CD8. Biochemical analysis using purif ied antiserum against 8HS-20 oligopeptides indicates that the gene enc odes proteins with mol. wts of 13.5, 14, 15.5 and 16 kDa, which associ ate with mu chains in pre-B cell lines, and that these molecules are e xpressed concomitantly with VpreB-1 and lambda5 gene products in the s ame cell lines.