Transcription of the blk gene in human B lymphocytes is controlled by two promoters.
Genomic DNA containing the first exon and 5'-flanking region of the human protein tyrosine kinase, blk, was isolated. Sequence analysis identified a TG repeat element in this region with enhancer activity, but no TATA or CCAAT sequences were found. Two blk transcripts of 2.2 and 2.5 kilobases were identified in various B-cell lines by Northern blot analyses, and primer extension experiments demonstrated two clusters of multiple transcription start sites. Subsequent promoter analyses by transient transfection assays with a reporter gene identified two promoter elements in the human blk gene. Promoter P1 contains sequences that have been shown to regulate the expression of immunoglobulin genes and promoter P2 contains elements that are highly conserved in the promoter of major histocompatibility complex class II genes, as well as a B-cell-specific activator protein- (BSAP) binding site. Electrophoretic mobility shift assays demonstrated that the binding of a protein to the BSAP-binding site was correlated with the presence of the 2.5-kilobase blk transcript. These data suggest that the two human blk RNAs arise from the transcription of the blk gene by two distinct promoters and that these promoters may be subject to regulation by different trans-acting factors.
Lin
Y H
YH
Department of Surgery, Stanford University School of Medicine, California 94305-5408, USA.
Shin
E J
EJ
Campbell
M J
MJ
Niederhuber
J E
JE
D001402:B-Lymphocytes / Q000166:cytology / Q000201:enzymology / Q000378:metabolism* / Q000473:pathology; D001483:Base Sequence; D001665:Binding Sites; D002460:Cell Line; D004252:DNA Mutational Analysis; D004268:DNA-Binding Proteins / Q000378:metabolism; D004742:Enhancer Elements, Genetic; D005091:Exons / Q000235:genetics; D005803:Genes, Immunoglobulin; D005802:Genes, MHC Class II; D017930:Genes, Reporter; D015698:Genomic Library; D006801:Humans; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000378:metabolism; D051757:PAX5 Transcription Factor; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D012333:RNA, Messenger / Q000235:genetics*; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis; D015183:Restriction Mapping; D017422:Sequence Analysis, DNA; D017384:Sequence Deletion; D014018:Tissue Distribution; D014157:Transcription Factors; D014158:Transcription, Genetic; D014162:Transfection; D019061:src-Family Kinases / Q000096:biosynthesis / Q000235:genetics*
D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D051757:PAX5 Transcription Factor; C497281:PAX5 protein, human; D012333:RNA, Messenger; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors; C082599:protein-tyrosine kinase p55(blk); D019061:src-Family Kinases