Cheng J F, Printz R, Callaghan T, Shuey D, Hardison R C
J Mol Biol. 1984 Jun 15;176(1):1-20. doi: 10.1016/0022-2836(84)90379-6.
The C repeat family was first observed in the rabbit beta-like gene family. We have estimated the repetition frequency of the C repeats, determined the nucleotide sequence of three intact members and one truncated member, and have investigated the size, tissue specificity, and intracellular localization of C repeat transcripts. Members of the C repeat family are short (average size of 316 base-pairs) and are repeated about 170,000 times per haploid genome in a widely dispersed pattern. They end in a 3' poly(dA) tract and are flanked by direct repeats that range in size from 8 to 16 base-pairs. The consensus internal control regions for polymerase III transcription are located near the 5' end. Different amounts of C repeat RNA accumulate in a variety of tissues, and most of the transcripts are confined to the nucleus. A heterogeneous distribution of C repeat RNA sizes was found, ranging from about 330 to 8200 nucleotides. These structural and transcriptional properties are similar to those of primate and rodent Alu and Alu-like repeats. However, the C repeats are not similar in sequence to the Alu repeats. Thus two different types of short, interspersed repeats capable of being transcribed and proposed to be transposable elements have now been identified in mammals. The positions of these short repeats in mammalian beta-like globin gene families are not tightly conserved.
C重复序列家族最初是在兔β样基因家族中观察到的。我们已经估计了C重复序列的重复频率，确定了三个完整成员和一个截短成员的核苷酸序列，并研究了C重复序列转录本的大小、组织特异性和细胞内定位。C重复序列家族的成员很短（平均大小为316个碱基对），在单倍体基因组中以广泛分散的模式重复约170,000次。它们以3'聚（dA）尾结束，并由大小从8到16个碱基对的同向重复序列侧翼。聚合酶III转录的共有内部控制区域位于5'端附近。不同组织中积累了不同量的C重复RNA，并且大多数转录本局限于细胞核。发现C重复RNA大小存在异质分布，范围从约330到8200个核苷酸。这些结构和转录特性与灵长类和啮齿类动物的Alu及Alu样重复序列相似。然而，C重复序列在序列上与Alu重复序列不同。因此，现在在哺乳动物中已经鉴定出两种不同类型的能够转录并被认为是可转座元件的短散在重复序列。这些短重复序列在哺乳动物β样珠蛋白基因家族中的位置并不严格保守。
