Schmidt E R, Godwin E A
EMBO J. 1983;2(7):1177-83. doi: 10.1002/j.1460-2075.1983.tb01564.x.
The nucleotide sequence of the non-transcribed spacer (NTS) in the ribosomal DNA (rDNA) of Chironomus thummi thummi and Chironomus thummi piger, including major parts of the external transcribed spacer, is described. The NTS of the two subspecies are very different in length, (thummi, 7 kb, piger, 2 kb); this is due to the insertion into the NTS of C.th. thummi of a large cluster of highly repetitive DNA sequences which are not present in the NTS of C. th. piger. The repetitive sequences, called Cla elements, are present in high copy number elsewhere in the genome of C. th. thummi and, in lower copy number, in the genome of C. th. piger in which they are mainly in the centromeric regions. Sequencing of the NTS of thummi and piger yielded information on the junctions between the Cla element cluster and the original NTS sequence, as well as on the sequence of the integration site before the transposition has occurred. The integration site is characterized by a dA cluster at the one end and a dT cluster at the other.
本文描述了嗜尸摇蚊指名亚种（Chironomus thummi thummi）和嗜尸摇蚊猪亚种（Chironomus thummi piger）核糖体DNA（rDNA）中非转录间隔区（NTS）的核苷酸序列，包括外部转录间隔区的主要部分。这两个亚种的NTS长度差异很大（嗜尸摇蚊指名亚种为7 kb，嗜尸摇蚊猪亚种为2 kb）；这是因为在嗜尸摇蚊指名亚种的NTS中插入了一大簇高度重复的DNA序列，而这些序列在嗜尸摇蚊猪亚种的NTS中不存在。这些重复序列被称为Cla元件，在嗜尸摇蚊指名亚种基因组的其他位置以高拷贝数存在，在嗜尸摇蚊猪亚种基因组中以较低拷贝数存在，主要位于着丝粒区域。对嗜尸摇蚊指名亚种和嗜尸摇蚊猪亚种NTS的测序产生了关于Cla元件簇与原始NTS序列之间连接的信息，以及转座发生前整合位点的序列信息。整合位点的特征是一端为dA簇，另一端为dT簇。
