Fillingham Jeffrey S, Pearlman Ronald E
Department of Biology, York University, Toronto, Ontario, Canada M3J 1P3.
Eukaryot Cell. 2004 Apr;3(2):288-301. doi: 10.1128/EC.3.2.288-301.2004.
Extensive programmed DNA rearrangements occur during the development of the somatic macronucleus from the germ line micronucleus in the sexual cycle of the ciliated protozoan Tetrahymena thermophila. Using an in vivo processing assay, we analyzed the role of micronucleus-limited DNA during the programmed deletion of mse2.9, an internal eliminated sequence (IES). We identified a 200-bp region within mse2.9 that contains an important cis-acting element which is required for the targeting of efficient programmed deletion. Our results, obtained with a series of mse2.9-based chimeric IESs, led us to suggest that the cis-acting elements in both micronucleus-limited and macronucleus-retained flanking DNAs stimulate programmed deletion to different degrees depending on the particular eliminated sequence. The mse2.9 IES is situated within the second intron of the micronuclear locus of the ARP1 gene. We show that the expression of ARP1 is not essential for the growth of Tetrahymena. Our results also suggest that mse2.9 is not subject to epigenetic regulation of DNA deletion, placing possible constraints on the scan RNA model of IES excision.
在嗜热四膜虫的有性生殖周期中，从生殖系小核发育为体细胞大核的过程中会发生广泛的程序性DNA重排。我们利用体内加工分析方法，分析了小核限定DNA在mse2.9（一种内部消除序列，IES）的程序性缺失过程中的作用。我们在mse2.9内鉴定出一个200 bp的区域，该区域包含一个重要的顺式作用元件，它是高效程序性缺失靶向所必需的。我们通过一系列基于mse2.9的嵌合IES获得的结果表明，小核限定和大核保留侧翼DNA中的顺式作用元件根据特定的消除序列不同程度地刺激程序性缺失。mse2.9 IES位于ARP1基因小核位点的第二个内含子内。我们表明，ARP1的表达对四膜虫的生长并非必需。我们的结果还表明，mse2.9不受DNA缺失的表观遗传调控，这对IES切除的扫描RNA模型施加了可能的限制。
