逆转座子的反式拼接 RNA 与着丝粒结合,调节玉米着丝粒染色质环。
Back-spliced RNA from retrotransposon binds to centromere and regulates centromeric chromatin loops in maize.
机构信息
State Key Laboratory of Plant Cell and Chromosome Engineering, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China.
University of Chinese Academy of Sciences, Beijing, China.
出版信息
PLoS Biol. 2020 Jan 29;18(1):e3000582. doi: 10.1371/journal.pbio.3000582. eCollection 2020 Jan.
In most plants, centromeric DNA contains highly repetitive sequences, including tandem repeats and retrotransposons; however, the roles of these sequences in the structure and function of the centromere are unclear. Here, we found that multiple RNA sequences from centromeric retrotransposons (CRMs) were enriched in maize (Zea mays) centromeres, and back-spliced RNAs were generated from CRM1. We identified 3 types of CRM1-derived circular RNAs with the same back-splicing site based on the back-spliced sequences. These circular RNAs bound to the centromere through R-loops. Two R-loop sites inside a single circular RNA promoted the formation of chromatin loops in CRM1 regions. When RNA interference (RNAi) was used to target the back-splicing site of the circular CRM1 RNAs, the levels of R-loops and chromatin loops formed by these circular RNAs decreased, while the levels of R-loops produced by linear RNAs with similar binding sites increased. Linear RNAs with only one R-loop site could not promote chromatin loop formation. Higher levels of R-loops and lower levels of chromatin loops in the CRM1 regions of RNAi plants led to a reduced localization of the centromeric H3 variant (CENH3). Our work reveals centromeric chromatin organization by circular CRM1 RNAs via R-loops and chromatin loops, which suggested that CRM1 elements might help build a suitable chromatin environment during centromere evolution. These results highlight that R-loops are integral components of centromeric chromatin and proper centromere structure is essential for CENH3 localization.
在大多数植物中,着丝粒 DNA 包含高度重复的序列,包括串联重复序列和反转录转座子;然而,这些序列在着丝粒的结构和功能中的作用尚不清楚。在这里,我们发现来自着丝粒反转座子(CRMs)的多个 RNA 序列在玉米(Zea mays)着丝粒中富集,并且从 CRM1 产生了反向剪接 RNA。我们基于反向剪接序列鉴定了 3 种具有相同反向剪接位点的 CRM1 衍生的环状 RNA。这些环状 RNA 通过 R 环与着丝粒结合。单个环状 RNA 内的两个 R 环位点促进了 CRM1 区域染色质环的形成。当使用 RNA 干扰 (RNAi) 靶向环状 CRM1 RNA 的反向剪接位点时,这些环状 RNA 形成的 R 环和染色质环的水平降低,而具有相似结合位点的线性 RNA 产生的 R 环水平增加。只有一个 R 环位点的线性 RNA 不能促进染色质环的形成。RNAi 植物中 CRM1 区域的 R 环和染色质环水平升高,导致着丝粒 H3 变体(CENH3)的定位减少。我们的工作通过 R 环和染色质环揭示了环状 CRM1 RNA 介导的着丝粒染色质组织,这表明 CRM1 元件可能有助于在着丝粒进化过程中建立合适的染色质环境。这些结果突出表明 R 环是着丝粒染色质的组成部分,适当的着丝粒结构对于 CENH3 的定位至关重要。