ANOMALOUS PLACEMENT OF INTRONS IN A MEMBER OF THE INTERMEDIATE FILAMENT MULTIGENE FAMILY - AN EVOLUTIONARY CONUNDRUM
ANOMALOUS PLACEMENT OF INTRONS IN A MEMBER OF THE INTERMEDIATE FILAMENT MULTIGENE FAMILY - AN EVOLUTIONARY CONUNDRUM
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DOI：
10.1128/mcb.6.5.1529
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发表时间：
1986-05-01
影响因子：
5.3
通讯作者：
COWAN, NJ
中科院分区：
文献类型：
--
作者：
LEWIS, SA;COWAN, NJ
内含子的起源和它们在基因表达、基因组进化和新表达序列产生中的作用（如果有的话）是人们知之甚少的问题。多基因家族为研究内含子的进化历史提供了一个有利的机会，因为它可以识别内含子位置和内容的变化，因为家族成员从一个共同的祖先序列的分歧。在这里，我们报告的68千道尔顿（kDa）的神经丝蛋白编码基因的完整序列，该基因是一个成员的中间丝多基因家族，分歧超过6亿年的年龄。该家族的其他五个成员（结蛋白、波形蛋白、胶质细胞酸性蛋白和I型和II型角蛋白）由在同源位置具有六个或更多个内含子的基因编码。令我们惊讶的是，在68 kDa的神经丝蛋白基因的内含子的数量和位置是完全异常的，只有三个内含子，其中没有一个对应的位置在任何特征的中间丝基因的内含子。这一发现是更加出乎意料的，因为比较氨基酸序列数据表明，68 kDa的神经丝蛋白结蛋白，波形蛋白，和胶质细胞酸性蛋白比这三种蛋白质和角蛋白之间的关系更密切。看来可能是mRNA介导的转座事件参与了68 kDa神经丝蛋白基因的进化，随后的事件导致了当代序列中三个内含子中至少两个的获得。
The origin of introns and their role (if any) in gene expression, in the evolution of the genome, and in the generation of new expressed sequences are issues that are understood poorly, it at all. Mutigene families provide a favorable opportunity for examining the evolutionary history of introns because it is possible to identify changes in intron placement and content since the divergence of family members from a common ancestral sequence. Here we report the complete sequence of the gene encoding the 68-kilodalton (kDa) neurofilament protein; the gene is a member of the intermediate filament multigene family that diverged over 600 million years age. Five other members of this family (desmin, vimentin, glial fibrillary acidic protein, and type I and type II keratins) are encoded by genes with six or more introns at homologous positions. To our surprise, the number and placement of introns in the 68-kDa neurofilament protein gene were completely anomalous, with only three introns, none of which corresponded in position to introns in any characterized intermediate filament gene. This finding was all the more unexpected because comparative amino acid sequence data suggest a closer relationship of the 68-kDa neurofilament proteins to desmin, vimentin, and glial fibrillary acidic protein than between any of these three proteins and the keratins. It appears likely that an mRNA-mediated transposition event was involved in the evolution of the 68-kDa neurofilament protein gene and that subsequent events led to the acquistion of at least two of the three introns present in the contemporary sequence.