Laboratory of Cell Function and Structure, Graduate School of Agricultural Science, Kobe University, Nada Kobe, Japan.
Department of Applied Biological Science, Faculty of Science and Technology, Tokyo University of Science, Noda, Chiba, Japan.
Commun Biol. 2021 Mar 19;4(1):351. doi: 10.1038/s42003-021-01836-5.
Transposable elements are common targets for transcriptional and post-transcriptional gene silencing in eukaryotic genomes. However, the molecular mechanisms responsible for sensing such repeated sequences in the genome remain largely unknown. Here, we show that machinery of homologous recombination (HR) and RNA silencing play cooperative roles in copy number-dependent de novo DNA methylation of the retrotransposon MAGGY in the fungus Pyricularia oryzae. Genetic and physical interaction studies revealed that RecA domain-containing proteins, including P. oryzae homologs of Rad51, Rad55, and Rad57, together with an uncharacterized protein, Ddnm1, form complex(es) and mediate either the overall level or the copy number-dependence of de novo MAGGY DNA methylation, likely in conjunction with DNA repair. Interestingly, P. oryzae mutants of specific RNA silencing components (MoDCL1 and MoAGO2) were impaired in copy number-dependence of MAGGY methylation. Co-immunoprecipitation of MoAGO2 and HR components suggested a physical interaction between the HR and RNA silencing machinery in the process.
转座元件是真核生物基因组中转录和转录后基因沉默的常见靶点。然而，负责感知基因组中这些重复序列的分子机制在很大程度上仍然未知。在这里，我们表明同源重组 (HR) 机制和 RNA 沉默在真菌稻瘟病菌中转座子 MAGGY 的拷贝数依赖性从头 DNA 甲基化中发挥协同作用。遗传和物理相互作用研究表明，包含 P. oryzae Rad51、Rad55 和 Rad57 同源物在内的 RecA 结构域蛋白以及一个未鉴定的蛋白 Ddnm1 形成复合物，并介导从头 MAGGY DNA 甲基化的整体水平或拷贝数依赖性，可能与 DNA 修复有关。有趣的是，特定 RNA 沉默成分（MoDCL1 和 MoAGO2）的 P. oryzae 突变体在 MAGGY 甲基化的拷贝数依赖性方面存在缺陷。MoAGO2 和 HR 成分的共免疫沉淀表明，在该过程中 HR 和 RNA 沉默机制之间存在物理相互作用。
