O'Hare K, Chadwick B P, Constantinou A, Davis A J, Mitchelson A, Tudor M
Department of Biochemistry, Imperial College of Science, Technology and Medicine, London SW7 2AZ, UK.
Mol Genet Genomics. 2002 Jul;267(5):647-55. doi: 10.1007/s00438-002-0698-x. Epub 2002 Jun 18.
We present an analysis of a chromosomal walk in the region of the euchromatin-heterochromatin transition at the base of the X chromosome of Drosophila melanogaster. This region is difficult to analyse because of the presence of repeated sequences, and we have used cosmids to walk from the last euchromatic gene, suppressor of forked, towards the pericentric heterochromatin. The proximal 30-kb sequence we have isolated consists of repetitive DNA, including four tandem copies of a 5.9-kb sequence. This tandem repeat is itself a mosaic of other, mostly repeated, sequences, including part of a retrotransposon without long terminal repeats, a simple-sequence region of TAA repeats and part of a retrotransposon with long terminal repeats that has not been previously described. Although sequences homologous to these components are found elsewhere in the genome, this arrangement of repeated sequences is only found at the base of the X chromosome. It is conserved in D. melanogaster strains of different geographic origin, but is not conserved in even closely related species.
我们对果蝇X染色体基部常染色质-异染色质转变区域的染色体步移进行了分析。由于存在重复序列，该区域难以分析，我们使用黏粒从最后一个常染色质基因——叉毛抑制基因开始，向近心端异染色质进行步移。我们分离出的近端30 kb序列由重复DNA组成，包括一个5.9 kb序列的四个串联拷贝。这个串联重复序列本身又是其他序列（大多为重复序列）的镶嵌体，包括一个没有长末端重复序列的反转录转座子的一部分、一个TAA重复的简单序列区域以及一个此前未描述过的有长末端重复序列的反转录转座子的一部分。尽管与这些组分同源的序列在基因组其他地方也能找到，但这种重复序列的排列仅在X染色体基部发现。它在不同地理来源的黑腹果蝇品系中保守，但在即使亲缘关系很近的物种中也不保守。
