CXXC1 is not essential for normal DNA double-strand break formation and meiotic recombination in mouse.
CXXC1 is not essential for normal DNA double-strand break formation and meiotic recombination in mouse.
复制标题
CXXC1对于小鼠中正常的DNA双链断裂形成和减数分裂重组并不是必需的。
DOI：
10.1371/journal.pgen.1007657
复制
发表时间：
2018-10
期刊：
影响因子：
4.5
通讯作者：
Petkov PM
中科院分区：
文献类型：
--
作者：
Tian H;Billings T;Petkov PM
在大多数哺乳动物中，包括小鼠和人类，减数分裂重组是由减数分裂特异性组蛋白甲基转移酶 PRDM9 决定的，该酶与特定 DNA 序列结合，并使组蛋白 3 在邻近核小体的赖氨酸 4 和赖氨酸 36 处三甲基化。这些作用确保了形成染色体轴的蛋白质结构上发生的 DNA 双链断裂成功形成和修复。热点与轴在被 PRDM9 激活后的关联过程知之甚少。此前，我们和其他人已经将哺乳动物中酿酒酵母 Spp1 的直系同源物 CXXC1 鉴定为 PRDM9 相互作用子。在酵母中，Spp1 是一种组蛋白甲基读取器，它将 H3K4me3 位点与重组机制连接起来，促进 DSB 形成。在这里，我们研究了 CXXC1 在小鼠减数分裂中是否具有类似的功能。我们创建了两种 Cxxc1 条件敲除小鼠模型，以在生殖细胞中以及减数分裂开始之前普遍消除 CXXC1。令人惊讶的是，雄性基因敲除小鼠具有生育能力，并且精母细胞中 CXXC1 的缺失对 PRDM9 热点三甲基化、双链断裂形成或修复没有影响。我们的结果表明，CXXC1 不是 PRDM9 激活的重组热点位点和 DSB 机制之间的重要联系，并且小鼠中的热点识别途径独立于 CXXC1。减数分裂重组通过确保等位基因的新组合正确传递给下一代来增加遗传多样性。在大多数哺乳动物中，减数分裂重组位点由组蛋白甲基转移酶 PRDM9 决定。这些位点被认为在其他蛋白质的参与下与染色体轴相关联，并经历双链断裂，并通过同源重组进行修复。在芽殖酵母中，Spp1（CXXC1 的直系同源物）与甲基化的 H3K4 结合，并将这些位点与促进 DSB 形成的染色体轴连接起来。然而，我们的数据表明，尽管 CXXC1 与雄性生殖细胞中的 PRDM9 相互作用，但它在小鼠减数分裂重组中并不发挥关键作用。这些结果表明，与酵母不同，包含 CXXC1 的重组起始途径只能作为小鼠减数分裂中的非必需途径。
In most mammals, including mice and humans, meiotic recombination is determined by the meiosis specific histone methytransferase PRDM9, which binds to specific DNA sequences and trimethylates histone 3 at lysine-4 and lysine-36 at the adjacent nucleosomes. These actions ensure successful DNA double strand break formation and repair that occur on the proteinaceous structure forming the chromosome axis. The process of hotspot association with the axis after their activation by PRDM9 is poorly understood. Previously, we and others have identified CXXC1, an ortholog of S. cerevisiae Spp1 in mammals, as a PRDM9 interactor. In yeast, Spp1 is a histone methyl reader that links H3K4me3 sites with the recombination machinery, promoting DSB formation. Here, we investigated whether CXXC1 has a similar function in mouse meiosis. We created two Cxxc1 conditional knockout mouse models to deplete CXXC1 generally in germ cells, and before the onset of meiosis. Surprisingly, male knockout mice were fertile, and the loss of CXXC1 in spermatocytes had no effect on PRDM9 hotspot trimethylation, double strand break formation or repair. Our results demonstrate that CXXC1 is not an essential link between PRDM9-activated recombination hotspot sites and DSB machinery and that the hotspot recognition pathway in mouse is independent of CXXC1. Meiotic recombination increases genetic diversity by ensuring novel combination of alleles passing correctly to the next generation. In most mammals, the meiotic recombination sites are determined by histone methyltransferase PRDM9. These sites are proposed to become associated with the chromosome axis with the participation of additional proteins and undergo double strand breaks, which are repaired by homologous recombination. In budding yeast, Spp1 (ortholog of CXXC1) binds to methylated H3K4 and connects these sites with the chromosome axis promoting DSB formation. However, our data suggest that even though CXXC1 interacts with PRDM9 in male germ cells, it does not play a crucial role in mouse meiotic recombination. These results indicate that, unlike in yeast, a recombination initiation pathway that includes CXXC1 could only serve as a non-essential pathway in mouse meiosis.