ISOLATION AND STRUCTURE OF A CDNA-ENCODING THE B1 (CD20) CELL-SURFACE ANTIGEN OF HUMAN LYMPHOCYTES-B
ISOLATION AND STRUCTURE OF A CDNA-ENCODING THE B1 (CD20) CELL-SURFACE ANTIGEN OF HUMAN LYMPHOCYTES-B
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DOI：
10.1073/pnas.85.1.208
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发表时间：
1988-01-01
影响因子：
11.1
通讯作者：
SAITO, H
中科院分区：
文献类型：
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作者：
TEDDER, TF;STREULI, M;SAITO, H
B1（CD 20）分子是人B淋巴细胞表面的一种Mr 33，000磷蛋白，可通过调节B细胞增殖和分化在体液免疫应答中发挥核心作用。在本报告中，分离了编码B1分子的cDNA克隆，并测定了B1的氨基酸序列。B细胞特异性的cDNA克隆，选择从人扁桃体cDNA文库通过与标记的cDNA来自大小分级的B细胞mRNA或大小分级的T细胞mRNA的差异杂交。在分离的261个cDNA克隆中，3个交叉杂交的cDNA克隆被选择作为编码B1的潜在候选者，基于它们与来自B1阳性细胞系的RNA的选择性杂交。最长的克隆，pB 1 -21，含有一个2.8-内切酶插入，具有一个891碱基对的开放阅读框架，编码33 kDa的蛋白质。在体外从pB 1 -21 cDNA克隆合成的mRNA被翻译成与B1具有相同表观分子量的蛋白质。 pB 1 -21翻译产物和B1的有限蛋白酶消化产生相同大小的肽，表明pB 1 -21 cDNA编码B1分子。凝胶印迹分析表明，pB 1 -21只在B1阳性细胞系中与2.8和3.4酶的两种mRNA杂交。从pB 1 -21核苷酸序列推导的氨基酸序列显然缺乏信号序列，并含有三个广泛的疏水区。推导的B1氨基酸序列与其他已知蛋白没有明显的同源性。
The B1 (CD20) molecule is a Mr 33,000 phosphoprotein on the surface of human B lymphocytes that may serve a central role in the humoral immune response by regulating B-cell proliferation and differentiation. In this report, a cDNA clone that encodes the B1 molecule was isolated and the amino acid sequence of B1 was determined. B-cell-specific cDNA clones were selected from a human tonsillar cDNA library by differential hybridization with labeled cDNA derived from either size-fractionated B-cell mRNA or size-fractionated T-cell mRNA. Of the 261 cDNA clones isolated, 3 cross-hybridizing cDNA clones were chosen as potential candidates for encoding B1 based on their selective hybridization to RNA from B1-positive cell lines. The longest clone, pB1-21, contained a 2.8-kilobase insert with an 891-base-pair open reading frame that encodes a protein of 33 kDa. mRNA synthesized from the pB1-21 cDNA clone in vitro was translated into a protein of the same apparent molecular weight as B1. Limited proteinase digestion of the pB1-21 translation product and B1 generated peptides of the same sizes, indicating that the pB1-21 cDNA encodes the B1 molecule. Gel blot analysis indicated that pB1-21 hybridized with two mRNA species of 2.8 and 3.4 kilobases only in B1-positive cell lines. The amino acid sequence deduced from the pB1-21 nucleotide sequence apparently lacks a signal sequence and contains three extensive hydrophobic regions. The deduced B1 amino acid sequence shows no significant homology with other known proteins.