Voliva C F, Martin S L, Hutchison C A, Edgell M H
J Mol Biol. 1984 Oct 5;178(4):795-813. doi: 10.1016/0022-2836(84)90312-7.
We have determined the complete nucleotide sequence for five members of the L1Md repetitive family from the beta-globin gene region of the BALB/c mouse. The five repeats are different lengths, each terminating at the 5' end at different points with respect to one another. We have analyzed the nucleotides around the endpoints of the five repeats for clues as to the mechanisms involved with the dispersal and 5' truncation of this repeat family. Each L1 member is flanked by a pair of short direct repeats. Since these direct repeats differ in length and sequence in each of the five cases, the dispersal mechanism does not involve a sequence targeted process. The sequence at the 3' end is conserved and its organization resembles the 3' end of a polyadenylated RNA, suggesting that transcripts of the repeat are involved in the dispersal process either directly or as intermediates in the generation of complementary DNA copies of the sequence. One of the L1 repeats is a recent insertion, since it is found in the Hbbd chromosome, but not in the Hbbs chromosome. This suggests a dispersal process that has been active as recently as 4 million years ago.
我们已经确定了来自BALB/c小鼠β-珠蛋白基因区域的L1Md重复家族五个成员的完整核苷酸序列。这五个重复序列长度不同，彼此之间在5'端的终止点也不同。我们分析了这五个重复序列端点周围的核苷酸，以寻找有关该重复家族扩散和5'端截短机制的线索。每个L1成员两侧都有一对短的直接重复序列。由于这五个案例中每个案例的这些直接重复序列在长度和序列上都不同，因此扩散机制不涉及序列靶向过程。3'端的序列是保守的，其结构类似于多聚腺苷酸化RNA的3'端，这表明该重复序列的转录本要么直接参与扩散过程，要么作为该序列互补DNA拷贝生成过程中的中间体。其中一个L1重复序列是最近插入的，因为它存在于Hbbd染色体中，但不存在于Hbbs染色体中。这表明扩散过程在距今400万年前仍很活跃。
