Lhuillier-Akakpo Maoussi, Frapporti Andrea, Denby Wilkes Cyril, Matelot Mélody, Vervoort Michel, Sperling Linda, Duharcourt Sandra
Institut Jacques Monod, CNRS, UMR 7592, Université Paris Diderot, Sorbonne Paris Cité, Paris, France; Sorbonne Universités, UPMC Univ., IFD, Paris, France.
Institut Jacques Monod, CNRS, UMR 7592, Université Paris Diderot, Sorbonne Paris Cité, Paris, France.
PLoS Genet. 2014 Sep 25;10(9):e1004665. doi: 10.1371/journal.pgen.1004665. eCollection 2014 Sep.
In the ciliate Paramecium tetraurelia, differentiation of the somatic nucleus from the zygotic nucleus is characterized by massive and reproducible deletion of transposable elements and of 45,000 short, dispersed, single-copy sequences. A specific class of small RNAs produced by the germline during meiosis, the scnRNAs, are involved in the epigenetic regulation of DNA deletion but the underlying mechanisms are poorly understood. Here, we show that trimethylation of histone H3 (H3K27me3 and H3K9me3) displays a dynamic nuclear localization that is altered when the endonuclease required for DNA elimination is depleted. We identified the putative histone methyltransferase Ezl1 necessary for H3K27me3 and H3K9me3 establishment and show that it is required for correct genome rearrangements. Genome-wide analyses show that scnRNA-mediated H3 trimethylation is necessary for the elimination of long, repeated germline DNA, while single copy sequences display differential sensitivity to depletion of proteins involved in the scnRNA pathway, Ezl1- a putative histone methyltransferase and Dcl5- a protein required for iesRNA biogenesis. Our study reveals cis-acting determinants, such as DNA length, also contribute to the definition of germline sequences to delete. We further show that precise excision of single copy DNA elements, as short as 26 bp, requires Ezl1, suggesting that development specific H3K27me3 and H3K9me3 ensure specific demarcation of very short germline sequences from the adjacent somatic sequences.
在纤毛虫四膜虫中，体细胞型细胞核从合子型细胞核的分化特征是转座元件以及45,000个短的、分散的单拷贝序列大量且可重复地缺失。生殖系在减数分裂过程中产生的一类特定的小RNA，即scnRNAs，参与DNA缺失的表观遗传调控，但其潜在机制尚不清楚。在这里，我们表明组蛋白H3的三甲基化（H3K27me3和H3K9me3）呈现出动态的核定位，当DNA消除所需的核酸内切酶缺失时，这种定位会发生改变。我们鉴定出了H3K27me3和H3K9me3建立所必需的假定组蛋白甲基转移酶Ezl1，并表明它对于正确的基因组重排是必需的。全基因组分析表明，scnRNA介导的H3三甲基化对于消除长的、重复的生殖系DNA是必需的，而单拷贝序列对scnRNA途径中相关蛋白（Ezl1，一种假定的组蛋白甲基转移酶；Dcl5，iesRNA生物合成所需的一种蛋白）缺失的敏感性存在差异。我们的研究揭示，顺式作用决定因素，如DNA长度，也有助于确定要删除的生殖系序列。我们进一步表明，短至26 bp的单拷贝DNA元件的精确切除需要Ezl1，这表明发育特异性的H3K27me3和H3K9me3确保了非常短的生殖系序列与相邻体细胞序列的特异性划分。
