嗜热四膜虫中一个接合特异性基因的多个内含子。
Multiple introns in a conjugation-specific gene from Tetrahymena thermophila.
作者信息
Martindale D W, Taylor F M
机构信息
Department of Microbiology, Macdonald College of McGill University, Ste Anne de Bellevue, PQ, Canada.
出版信息
Nucleic Acids Res. 1988 Mar 25;16(5):2189-201. doi: 10.1093/nar/16.5.2189.
Multiple introns have been found in a gene from a ciliated protozoan. This Tetrahymena thermophila gene (cnjB) is large (7.5 kb mRNA) and active only during conjugation, the organism's sexual cycle. Six introns ranging in size from 62 bp to 676 bp were found when we sequenced a 3.1 kb segment of the cnjB gene together with its corresponding cDNA. We estimate, by extrapolation of our current data, a total of approximately 30 introns in this gene with a total gene size (introns plus exons) of 15 kb or more. The number of introns is surprising given the scarcity of introns in ciliate genes examined to date. Our findings constitute the first example of multiple introns in a ciliate gene. Having the sequence of several introns has allowed us to construct consensus sequences for T. thermophila mRNA introns. The 5' and 3' intron junctions resemble those of general nuclear mRNA (GT/AG rule is followed) but differences are seen. In particular, stretches of 10 or more adenines and thymines are found adjacent to the conserved GT and AGs at the junctions. Unusual aspects of the coding region of this gene are discussed.
在一种纤毛原生动物的基因中发现了多个内含子。这个嗜热四膜虫基因（cnjB）很大（mRNA为7.5 kb），并且仅在该生物体的有性周期即接合期间才活跃。当我们对cnjB基因的一个3.1 kb片段及其相应的cDNA进行测序时，发现了6个大小从62 bp到676 bp不等的内含子。根据我们目前的数据推断，我们估计该基因总共约有30个内含子，基因总大小（内含子加外显子）为15 kb或更大。鉴于迄今为止所检测的纤毛虫基因中内含子很少，内含子的数量令人惊讶。我们的发现构成了纤毛虫基因中多个内含子的首个实例。拥有多个内含子的序列使我们能够构建嗜热四膜虫mRNA内含子的共有序列。5'和3'内含子连接点与一般核mRNA的连接点相似（遵循GT/AG规则），但也存在差异。特别是，在连接点处保守的GT和AG旁边发现了10个或更多的腺嘌呤和胸腺嘧啶序列。本文还讨论了该基因编码区的异常情况。
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