Experimental Teaching Center, Chongqing Medical University, No.1, Medical College Road, Chongqing, 400016, People's Republic of China.
Parasitol Res. 2013 Mar;112(3):1011-20. doi: 10.1007/s00436-012-3223-0. Epub 2012 Dec 20.
Microsporidia are a group of obligate intracellular parasites of medical and agricultural importance, which can infect almost all animals, including human beings. Using the genome data of Nosema bombycis, four families of miniature inverted-repeat transposable elements (MITEs) in ribosomal DNA (rDNA) were characterized in the microsporidian N. bombycis and were named LSUME1, ITSME1, SSUME1, and SSUME2, respectively. The genome-wide investigation of these MITEs shows that these MITEs families distribute randomly in N. bombycis genome. All insertion sequences have conserved characteristics of MITEs, the direct repeat sequence and terminal inverted-repeat sequence at both ends of each MITEs sequence. Additionally, using the CLC RNA Workbench Software, secondary structures of rRNA containing MITEs sequence have been predicted and were located in variable region or expansion segment. Furthermore, using two different probes, one is prepared by MITE sequence only (short probe) and the other is prepared by MITE sequence flanking partial rDNA sequence (long probe); northern blotting and dot blotting have been performed to detect the transcriptional and functional activity of the rDNA containing MITEs insertion. Fortunately, we found that the rDNA, which harbors the MITE, not only can be transcripted but also can form a complete ribosome. This is an interesting thing that one gene can keep active even when it has been inserted with another sequence. But the biological and structural significance of this observation is not readily apparent.
微孢子虫是一类具有医学和农业重要性的专性细胞内寄生虫，几乎可以感染所有动物，包括人类。利用 Nosema bombycis 的基因组数据，在微孢子虫 N. bombycis 中鉴定了核糖体 DNA（rDNA）中的四个微型倒置重复转座元件（MITE）家族，分别命名为 LSUME1、ITSME1、SSUME1 和 SSUME2。对这些 MITE 的全基因组调查表明，这些 MITE 家族在 N. bombycis 基因组中随机分布。所有插入序列都具有 MITE 的保守特征，即每个 MITE 序列两端的直接重复序列和末端反向重复序列。此外，使用 CLC RNA Workbench 软件，预测了含有 MITE 序列的 rRNA 的二级结构，并将其定位在可变区或扩展片段中。此外，使用两种不同的探针，一种是仅由 MITE 序列制备的探针（短探针），另一种是由 MITE 序列侧翼的部分 rDNA 序列制备的探针（长探针）；进行了 northern blot 和斑点印迹以检测含有 MITE 插入的 rDNA 的转录和功能活性。幸运的是，我们发现携带 MITE 的 rDNA 不仅可以转录，而且可以形成完整的核糖体。一个基因即使插入了另一个序列也能保持活性，这是一件有趣的事情。但是，这种观察的生物学和结构意义尚不清楚。
