Lee M G, Lewis S A, Wilde C D, Cowan N J
Cell. 1983 Jun;33(2):477-87. doi: 10.1016/0092-8674(83)90429-4.
A 3' untranslated region subclone from a human beta-tubulin cDNA clone has been used to dissect the human beta-tubulin multigene family. Four different beta-tubulin sequences were obtained. One consists of an expressed gene that yields two mRNA species of 1.8 kb and 2.6 kb as a consequence of alternative polyadenylation sites. The three remaining beta-tubulin sequences are all intronless pseudogenes, each containing a 3' poly(A) tract downstream from the poly(A) signal, and each flanked by a different short direct repeat. Two of these sequences were derived by integration into the host germ line of cDNA copies of the 1.8 kb mRNA; the third was derived from the 2.6 kb mRNA. Comparison of the functional and nonfunctional sequences suggests that the integration events took place 4, 10, and 13 million years ago. We anticipate that, in multigene families where germ-line expression occurs, a significant portion of sequences will be accounted for by pseudogenes generated via an RNA intermediate.
来自人β-微管蛋白cDNA克隆的一个3'非翻译区亚克隆已被用于剖析人β-微管蛋白多基因家族。获得了四种不同的β-微管蛋白序列。一种由一个表达基因组成，由于可变聚腺苷酸化位点，该基因产生1.8 kb和2.6 kb的两种mRNA。其余三种β-微管蛋白序列均为无内含子假基因，每个假基因在聚腺苷酸化信号下游含有一个3'聚（A）尾，且每个假基因两侧都有不同的短直接重复序列。其中两个序列是通过1.8 kb mRNA的cDNA拷贝整合到宿主种系中产生的；第三个序列来自2.6 kb mRNA。功能序列和非功能序列的比较表明，整合事件分别发生在400万、1000万和1300万年前。我们预计，在发生种系表达的多基因家族中，很大一部分序列将由通过RNA中间体产生的假基因组成。
