Unit of Human Parasite Molecular and Cell Biology, Key Laboratory of Molecular Virology and Immunology, Institut Pasteur of Shanghai, University of Chinese Academy of Sciences, Chinese Academy of Sciences, 200031 Shanghai, People's Republic of China.
School of Life Science and Technology, ShanghaiTech University, 201210 Shanghai, People's Republic of China.
Proc Natl Acad Sci U S A. 2019 Feb 19;116(8):3177-3182. doi: 10.1073/pnas.1811766116. Epub 2019 Feb 6.
The gene family encodes ∼60 surface antigens by which parasites escape the host immune responses via clonal expression of genes. However, the mechanism controlling this mutual exclusivity, associated with alterations in chromatin assembly, is not understood. Here, we determined how expression of the gene family is regulated by two RecQ DNA helicase family members, PfRecQ1 and PfWRN, in Through genetic manipulation, we found that the complete repertoire was silenced on knockout, whereas their expression did not show noticeable changes when was knocked out. More important, mutually exclusive expression of genes could be rescued by complementation of PfRecQ1. In addition, knocking out either of these two helicase genes changed the perinuclear cluster distribution of subtelomeres and subtelomeric genes. Whereas deletion of increased the heterochromatin mark trimethylated (H3K9me3) at the transcription start site (TSS) of the gene , that deletion had no effect on the global distribution of H3K9me3 over gene bodies, including those for the genes. ChIP-seq assay showed that PfRecQ1 was enriched globally at the TSSs of all genes, whereas PfWRN-enriched regions occurred at the gene bodies of the gene family, but not of other genes or at TSSs of all genes. On deletion, the gene moved from the active perinuclear transcription region to a silenced region of the type. These findings imply that PfRecQ1, but not PfWRN, is essential for maintaining the clonal expression of genes.
基因家族通过克隆表达基因编码约 60 种表面抗原，使寄生虫逃避宿主免疫反应。然而，控制这种互斥性的机制与染色质组装的改变有关，目前尚不清楚。在这里，我们确定了两个 RecQ DNA 解旋酶家族成员 PfRecQ1 和 PfWRN 如何在Pf 中调控基因家族的表达。通过遗传操作，我们发现敲除后完整的基因库被沉默，而敲除时其表达没有明显变化。更重要的是，PfRecQ1 的互补可以挽救基因的相互排斥表达。此外，敲除这两个解旋酶基因中的任何一个都会改变端粒周围亚端粒和端粒基因的核周簇分布。虽然缺失增加了基因转录起始位点（TSS）的异染色质标记三甲基化（H3K9me3），但这种缺失对基因体上 H3K9me3 的全局分布没有影响，包括基因的 H3K9me3 全局分布。ChIP-seq 分析表明，PfRecQ1 在所有基因的 TSS 处都有全局富集，而 PfWRN 富集的区域发生在基因家族的基因体上，而不是其他基因或所有基因的 TSS 处。在缺失时，基因从活跃的核周转录区域移动到类型的沉默区域。这些发现表明 PfRecQ1 而不是 PfWRN 对于维持基因的克隆表达是必不可少的。
