Origin of a "bridge" intron in the gene for a two-domain globin.
Origin of a "bridge" intron in the gene for a two-domain globin.
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双域珠蛋白基因中“桥”内含子的起源。
DOI：
10.1073/pnas.88.15.6672
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发表时间：
1991
影响因子：
11.1
通讯作者：
Riggs,AF
中科院分区：
文献类型：
--
作者：
Naito,Y;Riggs,CK;Vandergon,TL;Riggs,AF
蛤的红细胞表达两种血红蛋白，一种由16- 17-kDa链组成，另一种由35-kDa链组成。编码35-kDa链的cDNA的核苷酸序列表明，该多肽具有两个非常相似的血红素结合结构域，其在不使用额外的桥接序列的情况下连接。两个新的内含子出现在两个结构域珠蛋白的基因中：一个是“预编码”内含子，位于起始密码子5'的两个碱基处，另一个是“桥”内含子，将编码两个结构域的DNA序列分开。在预编码内含子的3'端和桥内含子的3'端之间以及在两结构域珠蛋白的cDNA的3'非编码区的部分和桥内含子的5'端之间存在密切的对应关系。这些观察结果表明，桥内含子产生的不平等交换两个相同或非常相似的基因之间的单域珠蛋白。这一结论，以及外显子最初是独立的“小基因”的提议[吉尔伯特，W. 03 The Dog of the Dog（1987）定量52，901-905]，表明许多内含子可能已经从一个基因的5'非编码区和/或第二个基因的3'非编码区进化而来。这一假设意味着剪接点与蛋白质的原始NH 2和COOH末端相关，并为剪接点通常映射到蛋白质表面的观察结果提供了解释。它们这样做是因为大多数NH 2-和COOH-末端残基通常位于蛋白质表面上或附近。
Red cells of the clam Barbatia reeveana express two hemoglobins, one composed of 16- to 17-kDa chains and the other of 35-kDa chains. The nucleotide sequence of the cDNA encoding the 35-kDa chain shows that the polypeptide has two very similar heme-binding domains, which are joined without use of an additional bridging sequence. Two novel introns occur in the gene for the two-domain globin: one, the "precoding" intron, is located two bases 5' from the start codon, and the other, a "bridge" intron, separates the DNA sequences encoding the two domains. Close correspondence exists between the 3' end of the precoding intron and the 3' end of the bridge intron and between parts of the 3' noncoding region of the cDNA for the two-domain globin and the 5' end of the bridge intron. These observations indicate that the bridge intron arose by unequal crossing-over between two identical or very similar genes for a single-domain globin. This conclusion, together with the proposal that exons were initially independent "minigenes" [Gilbert, W. (1987) Cold Spring Harbor Symp. Quant. Biol. 52, 901-905], suggests that many introns may have evolved from the 5' noncoding region of one gene and/or the 3' noncoding region of a second gene. This hypothesis implies that splice junctions would be associated with the original NH2 and COOH termini of proteins and provides an explanation for the observation that splice junctions usually map to protein surfaces. They do so because most NH2- and COOH-terminal residues are usually located on or near the surfaces of proteins.
影响因子：
4.3
作者：
H. Sambrook
通讯作者：
H. Sambrook