Kashiwamura S, Koyama T, Matsuo T, Steinmetz M, Kimoto M, Sakaguchi N
Department of Immunology, Saga Medical School, Japan.
J Immunol. 1990 Jul 1;145(1):337-43.
Genomic DNA clones containing the B cell-specific murine mb-1 gene were isolated and a 5.6-kb BamH I fragment was characterized. It is 5629 bp long and contains five exons: an exon containing the 5' untranslated and the coding sequence of the signal peptide, an exon of 294 bp, which contains most of the extracellular sequence of the MB-1 protein, a 119-bp long exon coding mainly for the transmembrane portion, and two exons of 69 bp and 427 bp encoding the cytoplasmic domain and the 3'-untranslated region, respectively. The mb-1 gene does not contain a "TATA box" found in many eukaryotic promoters. The 5'-flanking region has sequence stretches homologous to IgVH 5'-promoter regions and a bcl 2 intron sequence. It contains the decanucleotide sequence (ATGGCAAATA) almost identical to the octamer motif of IgVH promoters. A B cell-specific DNase I-hypersensitive site was found in the 3'-flanking region indicating that this region might be involved in B cell-specific expression of mb-1. Southern blot analysis of genomic liver DNA with the cloned mb-1 cDNA suggests the existence of another mb-1-related gene segment.
分离出了含有B细胞特异性小鼠mb-1基因的基因组DNA克隆，并对一个5.6kb的BamH I片段进行了特征分析。它长5629bp，包含五个外显子：一个包含5'非翻译区和信号肽编码序列的外显子，一个294bp的外显子，其包含MB-1蛋白的大部分细胞外序列，一个主要编码跨膜部分的119bp长的外显子，以及分别编码胞质结构域和3'非翻译区的69bp和427bp的两个外显子。mb-1基因不包含许多真核启动子中发现的“TATA盒”。5'侧翼区具有与IgVH 5'启动子区同源的序列延伸和一个bcl 2内含子序列。它包含与IgVH启动子的八聚体基序几乎相同的十核苷酸序列（ATGGCAAATA）。在3'侧翼区发现了一个B细胞特异性DNase I超敏位点，表明该区域可能参与mb-1的B细胞特异性表达。用克隆的mb-1 cDNA对基因组肝脏DNA进行Southern印迹分析表明存在另一个与mb-1相关的基因片段。
