Intron-encoded homing endonuclease I-TevI also functions as a transcriptional autorepressor
Intron-encoded homing endonuclease I-TevI also functions as a transcriptional autorepressor
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DOI：
10.1038/nsmb823
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发表时间：
2004-10-01
影响因子：
16.8
通讯作者：
Belfort, M
中科院分区：
文献类型：
--
作者：
Edgell, DR;Derbyshire, V;Belfort, M
内含子编码的归巢核酸内切酶的常规结合位点位于同源无内含子等位基因内，即所谓的归巢位点。在这里，我们描述了一种新的，高亲和力的结合位点I-TevI内切核酸酶，I组TD内含子的噬菌体T4内编码。该位点是与T4晚期启动子重叠的操纵子，T4晚期启动子从td内含子内驱动I-TevI表达。I-TevI以相等的亲和力结合操纵子和归巢位点，并作为转录自阻遏物发挥作用。催化结构域的不同序列和间隔要求导致操纵基因DNA上的切割活性降低。晶体学研究表明，DNA结合结构域与操纵子和归巢位点的总体相互作用是相似的，但有一些不同的氢键接触。我们提出了一个模型，其中蛋白质-DNA相互作用的灵活性允许I-TevI结合变体无内含子等位基因，以促进内含子的流动性，同时促进其在自动阻遏中的功能，从而在其宿主中的持久性。
Customary binding sites of intron-encoded homing endonucleases lie within cognate intronless alleles, at the so-called homing sites. Here, we describe a novel, high-affinity binding site for I-TevI endonuclease, encoded within the group I td intron of phage T4. This site is an operator that overlaps the T4 late promoter, which drives I-TevI expression from within the td intron. I-TevI binds the operator and homing sites with equal affinity, and functions as a transcriptional autorepressor. Distinct sequence and spacing requirements of the catalytic domain result in reduced cleavage activity on operator DNA. Crystallographic studies showed that the overall interactions of the DNA-binding domain with the operator and homing sites are similar, but have some different hydrogen-bonding contacts. We present a model in which the flexibility in protein-DNA interactions allows I-TevI to bind variant intronless alleles to promote intron mobility while facilitating its function in autorepression, and thereby persistence in its host.