A novel B-cell lineage-specific transcription factor present at early but not late stages of differentiation.
A novel B-cell-specific transcription factor, BSAP, was identified as a mammalian homolog of the sea urchin protein TSAP, which interacts with the promoters of four tissue-specific late histone H2A-2 and H2B-2 genes. As shown by mobility-shift, methylation interference, and mutational analyses, the mammalian protein BSAP recognizes all four sea urchin binding sites in a manner indistinguishable from TSAP; however, the two proteins differ in molecular weight. BSAP is exclusively restricted to the B-cell lineage of lymphoid differentiation. Its expression appears to be activated during pro-B-cell development, is abundant at the pre-B- and mature B-cell stages, but is absent in terminally differentiated plasma cells. Moreover, BSAP is clearly a B-cell-specific transcription factor, as a wild-type but not a mutant TSAP-binding site of the sea urchin functions only in transfected B cells as an upstream promoter element. Competition experiments did not reveal any high-affinity binding site for BSAP in known regulatory regions of immunoglobulin and class II major histocompatibility (MHC) genes, suggesting that BSAP is a regulator of a different set of B-lymphoid-specific genes.
Barberis
A
A
Institute of Molecular Pathology, Vienna, Austria.
Widenhorn
K
K
Vitelli
L
L
Busslinger
M
M
D000818:Animals; D001402:B-Lymphocytes / Q000166:cytology / Q000378:metabolism*; D001483:Base Sequence; D001665:Binding Sites; D002454:Cell Differentiation; D002460:Cell Line; D004247:DNA / Q000378:metabolism; D005803:Genes, Immunoglobulin; D005802:Genes, MHC Class II; D006801:Humans; D008969:Molecular Sequence Data; D008970:Molecular Weight; D011401:Promoter Regions, Genetic; D012045:Regulatory Sequences, Nucleic Acid; D012617:Sea Urchins; D014157:Transcription Factors / Q000378:metabolism*
D014157:Transcription Factors; D004247:DNA