The murine immunoglobulin alpha gene expresses multiple transcripts from a unique membrane exon.
The murine immunoglobulin alpha gene expresses multiple transcripts from a unique membrane exon.
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鼠免疫球蛋白α基因表达来自独特膜外显子的多个转录物。
DOI：
10.1002/j.1460-2075.1983.tb01518.x
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发表时间：
1983
期刊：
影响因子：
--
通讯作者：
Tucker,PW
中科院分区：
文献类型：
--
作者：
Word,CJ;Mushinski,JF;Tucker,PW
每一类免疫球蛋白重链都以膜型(M)和分泌型(S)两种形式存在，不同的基因片段编码不同的羧基末端序列。我们已经对BALB/c基因组克隆中的αm链羧基末端编码区的DNA进行了测序，并检测了转化的和正常的B细胞中αmRNA的表达。与其他有两个膜外显子(M1和M2)的小鼠重链基因不同，阿尔法基因只有一个膜外显子(阿尔法M1)。这个不同寻常的外显子编码一个高度保守的跨膜多肽和侧翼氨基酸，这些氨基酸是IgA独有的。阿尔法基因转录的复杂性也是不寻常的。在αM1下游，三个AATAAA六核苷酸被用来终止多达六个不同的阿尔法膜mRNAs。它们似乎只在其3‘-非翻译区的长度和剪接模式上不同，因此编码相同的αm蛋白。根据体外翻译判断，αS蛋白比αm蛋白小约4000道尔顿，由一个2.0kb的αS基因编码。我们认为，α-S和多个α-mRNAs的表达是在转录终止水平上的差异调控。
Immunoglobulin heavy chains of each class exist in two forms, membrane (m) and secreted (s), which have different carboxy‐terminal sequences encoded by different gene segments. We have sequenced the DNA spanning the coding region for the carboxy‐terminal end of the alpha m chain in a BALB/c genomic clone and have examined alpha mRNA expression in transformed and normal B cells. Unlike the other murine heavy chain genes, which have two membrane exons (M1 and M2), the alpha gene has only one membrane exon (alpha M1). This unusual exon encodes a highly conserved transmembranal peptide plus flanking amino acids singular to IgA. The complexity of the alpha gene transcription is also unusual. Downstream of alpha M1, three AATAAA hexanucleotides are used to terminate as many as six distinct alpha membrane mRNAs. These appear to differ only in length and splicing pattern of their 3′‐untranslated regions, and thus, encode the same alpha m protein. The alpha s protein is approximately 4000 daltons smaller than alpha m as judged by in vitro translation and is coded by a single 2.0‐kb alpha s mRNA. We propose that the expression of alpha s and the multiple alpha m mRNAs is differentially controlled at the level of transcriptional termination.