Distinct functions for the Drosophila piRNA pathway in genome maintenance and telomere protection.-猫眼课题宝

DOI：

10.1371/journal.pgen.1001246

发表时间：

2010-12-16

期刊：

PLoS genetics

影响因子：

4.5

通讯作者：

中科院分区：

生物学2区

文献类型：

作者：

Khurana JS;Xu J;Weng Z;Theurkauf WE

来源链接：

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3003142/?report=classic

转座子和其他自私的DNA元件可以在所有的门中找到，这些元件的移动可以损害基因组的完整性。皮尔纳（PIWI相互作用RNA）途径使生殖系中的转座子沉默，但尚不清楚该途径在发育过程中是否具有额外的功能。在这里，我们表明，突变的果蝇皮尔纳途径基因，armi，aub，ago 3，和rhi，导致广泛的分裂合子基因组在胚胎分裂的卵裂阶段。此外，aub和armi显示在减数分裂和分裂过程中端粒分辨率的缺陷;和lig-IV中的突变，破坏非同源末端连接，抑制这些融合。相比之下，lig-IV突变增强染色体断裂。染色质免疫沉淀研究表明，aub和armi突变破坏了HOAP的端粒结合，HOAP是端粒保护复合物的组分，并减少了19-至22-nt端粒特异性piRNA亚群的表达。相比之下，rh 1和ago 3中的突变不阻断HOAP结合或这些piRNA的产生。这些发现揭示了果蝇皮尔纳途径的遗传可分离功能。aub、armi、rhi和ago 3基因沉默转座子并在卵裂期胚胎分裂期间保持染色体完整性。然而，aub和armi基因在端粒保护复合物的组装中具有额外的功能。转座子和其他自私的遗传元件构成了所有真核生物基因组的重要部分，并且皮尔纳途径似乎在转座子沉默和基因组维持中具有保守的功能。然而，该途径的其他功能尚未得到充分探索。端粒必须受到保护，以免被修复机制识别为DNA断裂，修复机制可以共价连接未受保护的染色体末端，从而破坏减数分裂和有丝分裂染色体分离。我们表明，皮尔纳途径基因的一个子集中的突变破坏减数分裂和有丝分裂染色体分离，并且这些分离缺陷被阻断非同源DNA末端连接的突变抑制。这些突变也破坏了端粒保护复合物的组装，并减少了19- 22-nt端粒特异性RNA亚群的表达。因此，我们提出短piRNA的亚群指导端粒保护复合物的组装。

Transposons and other selfish DNA elements can be found in all phyla, and mobilization of these elements can compromise genome integrity. The piRNA (PIWI-interacting RNA) pathway silences transposons in the germline, but it is unclear if this pathway has additional functions during development. Here we show that mutations in the Drosophila piRNA pathway genes, armi, aub, ago3, and rhi, lead to extensive fragmentation of the zygotic genome during the cleavage stage of embryonic divisions. Additionally, aub and armi show defects in telomere resolution during meiosis and the cleavage divisions; and mutations in lig-IV, which disrupt non-homologous end joining, suppress these fusions. By contrast, lig-IV mutations enhance chromosome fragmentation. Chromatin immunoprecipitation studies show that aub and armi mutations disrupt telomere binding of HOAP, which is a component of the telomere protection complex, and reduce expression of a subpopulation of 19- to 22-nt telomere-specific piRNAs. Mutations in rhi and ago3, by contrast, do not block HOAP binding or production of these piRNAs. These findings uncover genetically separable functions for the Drosophila piRNA pathway. The aub, armi, rhi, and ago3 genes silence transposons and maintain chromosome integrity during cleavage-stage embryonic divisions. However, the aub and armi genes have an additional function in assembly of the telomere protection complex. Transposons and other selfish genetic elements make up a significant fraction of all eukaryotic genomes, and the piRNA pathway appears to have a conserved function in transposon silencing and genome maintenance. However, other functions for this pathway have not been fully explored. Telomeres must be protected from recognition as DNA breaks by the repair machinery, which can covalently ligate unprotected chromosome ends and thus disrupt meiotic and mitotic chromosome segregation. We show that mutations in a subset of piRNA pathway genes disrupt meiotic and mitotic chromosome separation and that these segregation defects are suppressed by a mutation that blocks ligation of non-homologous DNA ends. These mutations also disrupt assembly of the telomere protection complex and reduce expression of a subpopulation of 19- to 22-nt telomere-specific RNA. We therefore propose that a subpopulation of short piRNAs direct assembly of the telomere protection complex.