Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK.
Science. 2021 Jun 11;372(6547). doi: 10.1126/science.abe7500.
X-inactive specific transcript (Xist) RNA directs the process of X chromosome inactivation in mammals by spreading in cis along the chromosome from which it is transcribed and recruiting chromatin modifiers to silence gene transcription. To elucidate mechanisms of Xist RNA cis-confinement, we established a sequential dual-color labeling, super-resolution imaging approach to trace individual Xist RNA molecules over time, which enabled us to define fundamental parameters of spreading. We demonstrate a feedback mechanism linking Xist RNA synthesis and degradation and an unexpected physical coupling between preceding and newly synthesized Xist RNA molecules. Additionally, we find that the protein SPEN, a key factor for Xist-mediated gene silencing, has a distinct function in Xist RNA localization, stability, and coupling behaviors. Our results provide insights toward understanding the distinct dynamic properties of Xist RNA.
X 失活特异性转录本 (Xist) RNA 通过在顺式上沿着转录的染色体扩散，并招募染色质修饰物来沉默基因转录，从而指导哺乳动物的 X 染色体失活过程。为了阐明 Xist RNA 顺式限制的机制，我们建立了一种顺序双颜色标记、超分辨率成像方法，以随时间追踪单个 Xist RNA 分子，这使我们能够定义扩散的基本参数。我们证明了一种反馈机制，将 Xist RNA 的合成和降解联系起来，以及先前和新合成的 Xist RNA 分子之间出人意料的物理耦合。此外，我们发现蛋白 SPEN，Xist 介导基因沉默的关键因素，在 Xist RNA 定位、稳定性和偶联行为中具有独特的功能。我们的结果为理解 Xist RNA 的独特动态特性提供了思路。
