Sainz J, Cornudella L
Unidad de Química Macromolecular del CSIC, Universitat Politècnica de Catalunya, Barcelona, Spain.
Nucleic Acids Res. 1990 Feb 25;18(4):885-90. doi: 10.1093/nar/18.4.885.
The cloning and sequencing of a tandemly arrayed repetitive DNA sequence from the sea cucumber Holothuria tubulosa has been recently described (Sainz, J., Azorín, F. and Cornudella, L. 1989. Gene 80, 57-64). We have now searched the genomes of several echinoderm species for the presence of homologous repetitive elements. A close but not identical repeated sequence has been identified in a related holothuroid, H. polii. The monomeric repeat unit is 391 bp long and has a base composition of 66.8% A and T residues, lined up in tracts of 4 nt or larger. The monomeric sequence lacks any internal subrepeat organization although it displays a substantial degree of internal redundancy in the form of inverted and direct repeats. The repeated element accounts for 0.34% of the genome which corresponds to a repetition frequency of about 0.5 x 10(5) copies per haploid complement. The intra- and interspecific homologies among monomers of the satellite DNA as derived from sequence analyses are very high, averaging 97%. The results suggest that the homogeneity of the highly reiterated DNA sequence may be attributed to evolutionary conservative trends.
最近已报道了从管足海参（Holothuria tubulosa）中克隆和测序串联排列的重复DNA序列（Sainz, J., Azorín, F. 和 Cornudella, L. 1989. Gene 80, 57 - 64）。我们现在在几种棘皮动物的基因组中寻找同源重复元件的存在。在一种相关的海参（H. polii）中鉴定出了一个相近但不完全相同的重复序列。单体重复单元长391 bp，碱基组成为66.8%的A和T残基，以4个核苷酸或更长的片段排列。单体序列缺乏任何内部亚重复结构，尽管它以反向和正向重复的形式表现出相当程度的内部冗余。该重复元件占基因组的0.34%，这对应于每个单倍体基因组约0.5×10⁵个拷贝的重复频率。通过序列分析得出，卫星DNA单体之间的种内和种间同源性非常高，平均为97%。结果表明，高度重复的DNA序列的同质性可能归因于进化保守趋势。
