Elimination of foreign DNA during somatic differentiation in Tetrahymena thermophila shows position effect and is dosage dependent
Elimination of foreign DNA during somatic differentiation in Tetrahymena thermophila shows position effect and is dosage dependent
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DOI：
10.1128/ec.4.2.421-431.2005
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发表时间：
2005-02-01
期刊：
影响因子：
--
通讯作者：
Karrer, KM
中科院分区：
文献类型：
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作者：
Liu, YF;Song, XY;Karrer, KM
在纤毛虫四膜虫嗜热，大约15%的生殖细胞的微核DNA序列在体细胞大核的形成过程中被消除。绝大多数内部消除序列（IES）在微核基因组中重复，其中一些类似于转座因子。因此，有人认为DNA消除是作为去除入侵DNA的一种手段而进化的。在本研究中，细菌neo基因引入到生殖细胞微核从体细胞基因组中消除。两个不同位点的消除效率随着微核中neo基因拷贝数的增加而显著增加。neo消除的时间与内源性IEs相似，它们都产生消除元件的双向转录物，表明neo的缺失与内源性IEs的消除是通过相同的机制发生的。这些结果表明，在微核中的元素的重复提高其消除从新形成的体细胞基因组的嗜热四膜虫的效率。这些数据的功能和IES消除机制的影响进行了讨论。
In the ciliate Tetrahymena thermophila, approximately 15% of the germ line micronuclear DNA sequences are eliminated during formation of the somatic macronucleus. The vast majority of the internal eliminated sequences (IESs) are repeated in the micronuclear genome, and several of them resemble transposable elements. Thus, it has been suggested that DNA elimination evolved as a means for removing invading DNAs. In the present study, bacterial neo genes introduced into the germ line micronuclei were eliminated from the somatic genome. The efficiency of elimination from two different loci increased dramatically with the copy number of the neo genes in the micronuclei. The timing of neo elimination is similar to that of endogenous IESs, and they both produce bidirectional transcripts of the eliminated element, suggesting that the deletion of neo occurred by the same mechanism as elimination of endogenous IESs. These results indicate that repetition of an element in the micronucleus enhances the efficiency of its elimination from the newly formed somatic genome of Tetrahymena thermophila. The implications of these data in relation to the function and mechanism of IES elimination are discussed.