A circRNA from SEPALLATA3 regulates splicing of its cognate mRNA through R-loop formation
A circRNA from SEPALLATA3 regulates splicing of its cognate mRNA through R-loop formation
复制标题
DOI：
10.1038/nplants.2017.53
复制
发表时间：
2017-05-01
期刊：
影响因子：
18
通讯作者：
Conn, Simon J.
中科院分区：
文献类型：
--
作者：
Conn, Vanessa M.;Hugouvieux, Veronique;Conn, Simon J.
环状 RNA (circRNA) 是一类丰富多样的超稳定非规范 RNA，通过称为反向剪接的选择性剪接 (AS) 形式产生。这些单链、共价闭合的 circRNA 分子已在所有真核生命王国中得到鉴定(1)，但它们的功能仍然难以捉摸。在此，我们报告说，circRNA 可用作拟南芥中功能性、外显子跳过的 AS 变体的真正生物标志物，包括同源异型 MADS-box 转录因子家族。此外，我们证明源自 SEPALLATA3 (SEP3) 基因外显子 6 的 circRNA 增加了同源外显子跳跃 AS 变体（缺少外显子 6 的 SEP3.3）的丰度，进而驱动花同源异型表型。为了证明潜在的机制，我们发现 SEP3 外显子 6 circRNA 可以与其同源 DNA 位点强烈结合，形成 RNA：DNA 杂合体或 R 环，而线性 RNA 等效物与 DNA 的结合明显更弱。 R 环形成导致转录暂停，这已被证明与剪接因子招募和 AS(2-4) 一致。该报告提出了一种新颖的机制见解，揭示了至少一部分 circRNA 如何有助于提高其同源外显子跳跃信使 RNA 的剪接效率，并提供了由 circRNA 操作介导的有机体水平表型的第一个证据。
Circular RNAs (circRNAs) are a diverse and abundant class of hyper-stable, non-canonical RNAs that arise through a form of alternative splicing (AS) called back-splicing. These single-stranded, covalently-closed circRNA molecules have been identified in all eukaryotic kingdoms of life(1), yet their functions have remained elusive. Here, we report that circRNAs can be used as bona fide biomarkers of functional, exon-skipped AS variants in Arabidopsis, including in the homeotic MADS-box transcription factor family. Furthermore, we demonstrate that circRNAs derived from exon 6 of the SEPALLATA3 (SEP3) gene increase abundance of the cognate exon-skipped AS variant (SEP3.3 which lacks exon 6), in turn driving floral homeotic phenotypes. Toward demonstrating the underlying mechanism, we show that the SEP3 exon 6 circRNA can bind strongly to its cognate DNA locus, forming an RNA: DNA hybrid, or R-loop, whereas the linear RNA equivalent bound significantly more weakly to DNA. R-loop formation results in transcriptional pausing, which has been shown to coincide with splicing factor recruitment and AS(2-4). This report presents a novel mechanistic insight for how at least a subset of circRNAs probably contribute to increased splicing efficiency of their cognate exon-skipped messenger RNA and provides the first evidence of an organismal-level phenotype mediated by circRNA manipulation.