Saci-1, -2, and -3 and Perere, four novel retrotransposons with high transcriptional activities from the human parasite Schistosoma mansoni
Saci-1, -2, and -3 and Perere, four novel retrotransposons with high transcriptional activities from the human parasite Schistosoma mansoni
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DOI：
10.1128/jvi.78.6.2967-2978.2004
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发表时间：
2004-03-01
影响因子：
5.4
通讯作者：
Verjovski-Almeida, S
中科院分区：
文献类型：
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作者：
DeMarco, R;Kowaltowski, AT;Verjovski-Almeida, S
利用本课题组最近建立的曼氏血吸虫18万个表达序列标签(EST)的数据集，我们鉴定了三个新的长端重复序列(LTR)和一个新的非LTR表达的反转录转座子，分别命名为SacI-1、-2、-3和Perere。从EST中重构了全长序列，并推导出具有几个未被破坏的特征的开放阅读框(ORF)，表明它们可能是不同已知转座子家族中的活性反转录转座子。将重建的序列与可用的初步基因组序列数据进行比对，证实了转座子的整体结构。尾蚴的转座子转座子序列频率占该时期所有转录本的14%，比血吸虫高2倍，比成虫、卵、毛虫和生殖球高3-4倍。我们通过Southern印迹分析、EST注释和计数以及对来自基因表达社会分析文库的转座子标签的计数表明，这四个新的反转录转座子在基因组中的拷贝数比之前描述的四个曼氏链球菌反转录转座子的拷贝数低10-30倍，每个拷贝的转录速率高4-200倍。这些差异导致我们假设在曼氏血吸虫基因组中存在两种不同的反转录转座子群体，在其生态学中占据不同的生态位。在四个不同的曼氏葡萄球菌靶基因转录本的5‘和3’非翻译区中发现了反转录转座子片段插入的例子。这里提供的数据表明，这些元素在这种复杂的人类寄生虫基因组的动态中发挥了作用。
Using the data set of 180,000 expressed sequence tags (ESTs) of the blood fluke Schistosoma mansoni generated recently by our group, we identified three novel long-terminal-repeat (LTR)- and one novel non-LTR-expressed retrotransposon, named Saci-1, -2, and -3 and Perere, respectively. Full-length sequences were reconstructed from ESTs and have deduced open reading frames (ORFs) with several uncorrupted features, characterizing them as possible active retrotransposons of different known transposon families. Alignment of reconstructed sequences to available preliminary genome sequence data confirmed the overall structure of the transposons. The frequency of sequenced transposon transcripts in cercariae was 14% of all transcripts from that stage, twofold higher than that in schistosomula and three- to fourfold higher than that in adults, eggs, miracidia, and germ balls. We show by Southern blot analysis, by EST annotation and tallying, and by counting transposon tags from a Social Analysis of Gene Expression library, that the four novel retrotransposons exhibit a 10- to 30-fold lower copy number in the genome and a 4- to 200-fold-higher transcriptional rate per copy than the four previously described S. mansoni retrotransposons. Such differences lead us to hypothesize that there are two different populations of retrotransposons in S. mansoni genome, occupying different niches in its ecology. Examples of retrotransposon fragment inserts were found into the 5' and 3' untranslated regions of four different S. mansoni target gene transcripts. The data presented here suggest a role for these elements in the dynamics of this complex human parasite genome.