Department of Molecular, Cellular and Developmental Biology, University of California, Los Angeles (UCLA), Los Angeles, CA, 90095, USA.
Department of Microbiology, Faculty of Medicine, Chiang Mai University, Chiang Mai, 50200, Thailand.
Nat Commun. 2019 Sep 2;10(1):3916. doi: 10.1038/s41467-019-11759-9.
Transcription by RNA polymerase V (Pol V) in plants is required for RNA-directed DNA methylation, leading to transcriptional gene silencing. Global chromatin association of Pol V requires components of the DDR complex DRD1, DMS3 and RDM1, but the assembly process of this complex and the underlying mechanism for Pol V recruitment remain unknown. Here we show that all DDR complex components co-localize with Pol V, and we report the cryoEM structures of two complexes associated with Pol V recruitment-DR (DMS3-RDM1) and DDR' (DMS3-RDM1-DRD1 peptide), at 3.6 Å and 3.5 Å resolution, respectively. RDM1 dimerization at the center frames the assembly of the entire complex and mediates interactions between DMS3 and DRD1 with a stoichiometry of 1 DRD1:4 DMS3:2 RDM1. DRD1 binding to the DR complex induces a drastic movement of a DMS3 coiled-coil helix bundle. We hypothesize that both complexes are functional intermediates that mediate Pol V recruitment.
在植物中，由 RNA 聚合酶 V（Pol V）转录是 RNA 指导的 DNA 甲基化所必需的，导致转录基因沉默。Pol V 的全基因组染色质关联需要 DDR 复合物的成分 DRD1、DMS3 和 RDM1，但该复合物的组装过程和 Pol V 募集的潜在机制仍不清楚。在这里，我们表明所有 DDR 复合物成分都与 Pol V 共定位，并且我们报告了与 Pol V 募集相关的两个复合物的 cryoEM 结构-DR（DMS3-RDM1）和 DDR'（DMS3-RDM1-DRD1 肽），分辨率分别为 3.6 Å 和 3.5 Å。RDM1 二聚体在中心构成整个复合物的组装，并介导 DMS3 和 DRD1 之间的相互作用，其计量比为 1 DRD1:4 DMS3:2 RDM1。DRD1 与 DR 复合物的结合诱导 DMS3 卷曲螺旋束的剧烈运动。我们假设这两个复合物都是介导 Pol V 募集的功能中间产物。
