The Drosophila telomere-capping protein Verrocchio binds single-stranded DNA and protects telomeres from DNA damage response.
The Drosophila telomere-capping protein Verrocchio binds single-stranded DNA and protects telomeres from DNA damage response.
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DOI：
10.1093/nar/gkw1244
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发表时间：
2017-04-07
影响因子：
14.9
通讯作者：
Raffa GD
中科院分区：
文献类型：
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作者：
Cicconi A;Micheli E;Vernì F;Jackson A;Gradilla AC;Cipressa F;Raimondo D;Bosso G;Wakefield JG;Ciapponi L;Cenci G;Gatti M;Cacchione S;Raffa GD
果蝇端粒是一种不依赖于序列的结构，它是由三种特殊的逆转录元件转座到染色体末端而不是由端粒酶活性维持的。果蝇端粒受到包括HOAP、HipHop、Moi和Ver蛋白的末端蛋白复合物的保护。这些是快速进化的非保守蛋白质，仅在端粒定位和发挥作用，保护它们免受融合事件的影响。我们以前曾提出，终端是功能类似物的shelterin，多蛋白复合物，保护人类端粒。在这里，我们使用电泳迁移率变动分析（EMSA）和原子力显微镜（AFM）显示，Ver优先结合单链DNA（ssDNA），没有序列特异性。我们还表明，莫伊和Ver在体内形成一个复杂的。虽然这两种蛋白质在端粒上的定位是相互依赖的，但Moi既不结合ssDNA，也不促进Ver与ssDNA的结合。与这些结果相一致，我们发现Ver-depleted端粒形成RPA和γ H2 AX焦点，就像缺乏ssDNA结合POT 1蛋白的人类端粒一样。总的来说，我们的研究结果表明，果蝇端粒具有像其他真核生物一样的ssDNA悬垂，并且末端蛋白复合物在结构和功能上与shelterin相似。
Drosophila telomeres are sequence-independent structures maintained by transposition to chromosome ends of three specialized retroelements rather than by telomerase activity. Fly telomeres are protected by the terminin complex that includes the HOAP, HipHop, Moi and Ver proteins. These are fast evolving, non-conserved proteins that localize and function exclusively at telomeres, protecting them from fusion events. We have previously suggested that terminin is the functional analogue of shelterin, the multi-protein complex that protects human telomeres. Here, we use electrophoretic mobility shift assay (EMSA) and atomic force microscopy (AFM) to show that Ver preferentially binds single-stranded DNA (ssDNA) with no sequence specificity. We also show that Moi and Ver form a complex in vivo. Although these two proteins are mutually dependent for their localization at telomeres, Moi neither binds ssDNA nor facilitates Ver binding to ssDNA. Consistent with these results, we found that Ver-depleted telomeres form RPA and γH2AX foci, like the human telomeres lacking the ssDNA-binding POT1 protein. Collectively, our findings suggest that Drosophila telomeres possess a ssDNA overhang like the other eukaryotes, and that the terminin complex is architecturally and functionally similar to shelterin.