Lopes Fabrício R, Silva Joana C, Benchimol Marlene, Costa Gustavo G L, Pereira Gonçalo A G, Carareto Claudia M A
UNESP, São Paulo State University, Department of Biology, São José do Rio Preto, São Paulo, Brazil.
BMC Genomics. 2009 Jul 21;10:330. doi: 10.1186/1471-2164-10-330.
For three decades the Mutator system was thought to be exclusive of plants, until the first homolog representatives were characterized in fungi and in early-diverging amoebas earlier in this decade.
Here, we describe and characterize four families of Mutator-like elements in a new eukaryotic group, the Parabasalids. These Trichomonas vaginalis Mutator- like elements, or TvMULEs, are active in T. vaginalis and patchily distributed among 12 trichomonad species and isolates. Despite their relatively distinctive amino acid composition, the inclusion of the repeats TvMULE1, TvMULE2, TvMULE3 and TvMULE4 into the Mutator superfamily is justified by sequence, structural and phylogenetic analyses. In addition, we identified three new TvMULE-related sequences in the genome sequence of Candida albicans. While TvMULE1 is a member of the MuDR clade, predominantly from plants, the other three TvMULEs, together with the C. albicans elements, represent a new and quite distinct Mutator lineage, which we named TvCaMULEs. The finding of TvMULE1 sequence inserted into other putative repeat suggests the occurrence a novel TE family not yet described.
These findings expand the taxonomic distribution and the range of functional motif of MULEs among eukaryotes. The characterization of the dynamics of TvMULEs and other transposons in this organism is of particular interest because it is atypical for an asexual species to have such an extreme level of TE activity; this genetic landscape makes an interesting case study for causes and consequences of such activity. Finally, the extreme repetitiveness of the T. vaginalis genome and the remarkable degree of sequence identity within its repeat families highlights this species as an ideal system to characterize new transposable elements.
三十年来，诱变系统一直被认为是植物所特有的，直到本世纪初在真菌和早期分化的变形虫中首次鉴定出同源代表。
在这里，我们描述并鉴定了新的真核生物类群——副基足虫中的四类类Mutator元件。这些阴道毛滴虫类Mutator元件（TvMULEs）在阴道毛滴虫中具有活性，并且零散分布于12种毛滴虫物种和分离株中。尽管它们的氨基酸组成相对独特，但通过序列、结构和系统发育分析，将TvMULE1、TvMULE2、TvMULE3和TvMULE4重复序列归入Mutator超家族是合理的。此外，我们在白色念珠菌的基因组序列中鉴定出三个新的与TvMULE相关的序列。虽然TvMULE1是主要来自植物的MuDR进化枝的成员，但其他三个TvMULEs以及白色念珠菌的元件代表了一个新的且截然不同的Mutator谱系，我们将其命名为TvCaMULEs。TvMULE1序列插入其他假定重复序列的发现表明存在一个尚未描述的新型转座子家族。
这些发现扩展了真核生物中Mutator元件的分类分布和功能基序范围。阴道毛滴虫中TvMULEs和其他转座子动态特征的鉴定尤为有趣，因为无性物种具有如此高水平的转座子活性是非同寻常的；这种遗传格局为这种活性的原因和后果提供了一个有趣的案例研究。最后，阴道毛滴虫基因组的极端重复性及其重复家族内显著的序列同一性程度突出表明该物种是鉴定新转座元件的理想系统。
