Pena H B, de Souza C P, Simpson A J, Pena S D
Departamento de Bioquímica e Imunologia, Universidade Federal de Minas Grais, Belo Horizonte, Brazil.
Proc Natl Acad Sci U S A. 1995 Jan 31;92(3):915-9. doi: 10.1073/pnas.92.3.915.
It has been shown that the mtDNA of the parasitic trematode Schistosoma mansoni is hypervariable in size. We report here that this length variation is due to a large polymorphic minisatellite composed of two types of repeated sequences of 558 bp and 62 bp. Each minisatellite repeat is made up of a large 558-bp component and a variable tandem array of the small 62-bp unit. Of more fundamental interest was the finding that both the 558-bp and 62-bp components have significant homology with a gene, SM750, previously identified in the nuclear genome of S. mansoni. The small 62-bp unit is identical to the nuclear polymorphic repeat element, which is apparently spread throughout the nuclear genome and is abundant among transcripts, in addition to being present in five tandem copies in SM750. The presence, in the S. mansoni mtDNA, of fragments of genes that are present in and transcribed from the nuclear genome raises the question of the origin of these sequences. The arrangement and the variability that the mtDNA minisatellite embodies were explored as an identity test for S. mansoni based on the use of PCR for tallying the relative abundance of the several repeat numbers of the tandem arrays of the 62-bp unit within the minisatellite structure.
研究表明，寄生吸虫曼氏血吸虫的线粒体DNA（mtDNA）大小高度可变。我们在此报告，这种长度变异是由于一个大型多态性小卫星造成的，该小卫星由558 bp和62 bp两种重复序列组成。每个小卫星重复序列由一个大的558 bp组件和一个由小的62 bp单元组成的可变串联阵列构成。更具根本意义的发现是，558 bp和62 bp组件都与一个先前在曼氏血吸虫核基因组中鉴定出的基因SM750具有显著同源性。小的62 bp单元与核多态性重复元件相同，该元件显然遍布整个核基因组，在转录本中丰富，此外还以五个串联拷贝的形式存在于SM750中。曼氏血吸虫mtDNA中存在核基因组中存在并转录的基因片段，这就提出了这些序列的起源问题。基于使用聚合酶链反应（PCR）来计算小卫星结构内62 bp单元串联阵列的几个重复数的相对丰度，对mtDNA小卫星所体现的排列和变异性进行了探索，以此作为曼氏血吸虫的身份测试。
