Channel nuclear pore complex subunits are required for transposon silencing in Drosophila.
Channel nuclear pore complex subunits are required for transposon silencing in Drosophila.
复制标题
通道核孔复合体亚基是果蝇转座子沉默所必需的。
DOI：
10.7554/elife.66321
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发表时间：
2021-04-15
期刊：
影响因子：
7.7
通讯作者：
Czech B
中科院分区：
文献类型：
--
作者：
Munafò M;Lawless VR;Passera A;MacMillan S;Bornelöv S;Haussmann IU;Soller M;Hannon GJ;Czech B
核孔复合物（NPC）是细胞核和细胞质之间的主要通道，能够交换大分子货物。NPC由约30种不同核孔蛋白（Nups）的多个拷贝组成，充当选择性门户，与单独许可特定货物类别通过的因子相互作用。在这里，我们表明，两个Nups的内部通道，Nup 54和Nup 58，是必不可少的转座子沉默通过PIWI相互作用的RNA（皮尔纳）途径在果蝇卵巢。在卵泡细胞中，Nup 54和Nup 58的缺失导致仅来自弗拉门戈基因座的皮尔纳生物合成受损，而其他NPC亚基的敲除具有广泛的后果。这提供了证据表明，一些NUP可以在特定组织的情况下获得专门的角色。我们的研究结果巩固了这样的想法，即NPC的功能不仅仅是构成一个障碍，核/质交换的基因组位点受到强大的选择压力，可以利用NPC亚基，以促进其表达。转座子是一种基因序列，当它被激活时，可以在基因组中移动并插入新的位置。这可能会破坏细胞正常工作所需的信息：例如，在生殖器官中，转座子活动可能导致不育。因此，许多生物体都有控制转座子的细胞系统。动物细胞包括两个主要部分：细胞核，其中包含遗传信息，以及细胞质，其中发生生命所需的大多数化学反应。分子不断地在细胞核和细胞质之间移动，就像人们进出一个繁忙的忙碌火车站一样。两个隔间之间的连接“门”被称为核孔复合物（NPC），它们的工作是确保每个通过的分子到达正确的目的地。最近的研究表明，构成NPC的单个蛋白质（称为核孔蛋白）可能在细胞内发挥其他作用。特别是，对果蝇的遗传研究表明，一些核孔蛋白有助于控制卵巢内的转座子活性-但它们是如何做到这一点的仍然不清楚。因此，Munaflane等人开始确定核孔蛋白是否确实主动沉默转座子，或者这只是改变核-胞质转运的副作用。使用从果蝇卵巢生长的细胞进行的实验表明，耗尽两种特定的核孔蛋白Nup 54和Nup 58，重新激活转座子，对大多数基因或细胞的整体健康影响最小。这表明Nup 54和Nup 58在转座子沉默中起直接作用。此外，对缺乏Nup 54和Nup 58的细胞中基因表达的详细分析显示，一个基因的产物弗拉门戈确实受到了影响。通常情况下，弗拉门戈作为一个“总开关”关闭转座子。如果没有Nup 54和Nup 58，弗拉门戈编码的分子就无法到达胞质溶胶中的专用位置，因此无法执行其任务。这些结果表明，核孔蛋白不仅仅是细胞核的“看门人”，它还在适应体内各个组织中发挥着重要作用。进一步的研究将有助于确定其他生物是否也是如此，以及这些机制是否有助于了解人类疾病。
The nuclear pore complex (NPC) is the principal gateway between nucleus and cytoplasm that enables exchange of macromolecular cargo. Composed of multiple copies of ~30 different nucleoporins (Nups), the NPC acts as a selective portal, interacting with factors which individually license passage of specific cargo classes. Here we show that two Nups of the inner channel, Nup54 and Nup58, are essential for transposon silencing via the PIWI-interacting RNA (piRNA) pathway in the Drosophila ovary. In ovarian follicle cells, loss of Nup54 and Nup58 results in compromised piRNA biogenesis exclusively from the flamenco locus, whereas knockdowns of other NPC subunits have widespread consequences. This provides evidence that some Nups can acquire specialised roles in tissue-specific contexts. Our findings consolidate the idea that the NPC has functions beyond simply constituting a barrier to nuclear/cytoplasmic exchange as genomic loci subjected to strong selective pressure can exploit NPC subunits to facilitate their expression. Transposons are genetic sequences, which, when active, can move around the genome and insert themselves into new locations. This can potentially disrupt the information required for cells to work properly: in reproductive organs, for example, transposon activity can lead to infertility. Many organisms therefore have cellular systems that keep transposons in check. Animal cells comprise two main compartments: the nucleus, which contains the genetic information, and the cytosol, where most chemical reactions necessary for life take place. Molecules continually move between nucleus and cytosol, much as people go in and out of a busy train station. The connecting ‘doors’ between the two compartments are called Nuclear Pore Complexes (NPCs), and their job is to ensure that each molecule passing through reaches its correct destination. Recent research shows that the individual proteins making up NPCs (called nucleoporins) may play other roles within the cell. In particular, genetic studies in fruit flies suggested that some nucleoporins help to control transposon activity within the ovary – but how they did this was still unclear. Munafò et al. therefore set out to determine if the nucleoporins were indeed actively silencing the transposons, or if this was just a side effect of altered nuclear-cytosolic transport. Experiments using cells grown from fruit fly ovaries revealed that depleting two specific nucleoporins, Nup54 and Nup58, re-activated transposons with minimal effects on most genes or the overall health of the cells. This suggests that Nup54 and Nup58 play a direct role in transposon silencing. Further, detailed analysis of gene expression in Nup54- and Nup58-lacking cells revealed that the product of one gene, flamenco, was indeed affected. Normally, flamenco acts as a ‘master switch’ to turn off transposons. Without Nup54 and Nup58, the molecule encoded by flamenco could not reach its dedicated location in the cytosol, and thus could not carry out its task. These results show that, far from being mere ‘doorkeepers’ for the nucleus, nucleoporins play important roles adapted to individual tissues in the body. Further research will help determine if the same is true for other organisms, and if these mechanisms can help understand human diseases.