Mechanisms of Epigenetic Inheritance, Department of Developmental and Stem Cell Biology, Institut Pasteur, UMR 3738, CNRS, Paris, France.
Sorbonne Université, Collège doctoral, Paris, France.
Nat Cell Biol. 2020 Feb;22(2):235-245. doi: 10.1038/s41556-020-0462-7. Epub 2020 Feb 3.
PIWI-interacting RNAs (piRNAs) promote fertility in many animals. However, whether this is due to their conserved role in repressing repetitive elements (REs) remains unclear. Here, we show that the progressive loss of fertility in Caenorhabditis elegans lacking piRNAs is not caused by derepression of REs or other piRNA targets but, rather, is mediated by epigenetic silencing of all of the replicative histone genes. In the absence of piRNAs, downstream components of the piRNA pathway relocalize from germ granules and piRNA targets to histone mRNAs to synthesize antisense small RNAs (sRNAs) and induce transgenerational silencing. Removal of the downstream components of the piRNA pathway restores histone mRNA expression and fertility in piRNA mutants, and the inheritance of histone sRNAs in wild-type worms adversely affects their fertility for multiple generations. We conclude that sRNA-mediated silencing of histone genes impairs the fertility of piRNA mutants and may serve to maintain piRNAs across evolution.
PIWI 相互作用 RNA(piRNAs)在许多动物中促进生育能力。然而,其抑制重复元件(REs)的保守作用是否仍然不清楚。在这里,我们表明,缺乏 piRNAs 的秀丽隐杆线虫生育能力逐渐丧失不是由于 REs 或其他 piRNA 靶标被去抑制引起的,而是由所有复制组蛋白基因的表观遗传沉默介导的。在没有 piRNAs 的情况下,piRNA 途径的下游成分从生殖颗粒和 piRNA 靶标重新定位到组蛋白 mRNA 以合成反义小 RNA(sRNA)并诱导跨代沉默。去除 piRNA 途径的下游成分可恢复 piRNA 突变体中的组蛋白 mRNA 表达和生育能力,并且野生型蠕虫中组蛋白 sRNA 的遗传对其多个世代的生育能力有不利影响。我们得出结论,组蛋白基因的 sRNA 介导的沉默会损害 piRNA 突变体的生育能力,并且可能有助于在进化过程中维持 piRNAs。