Wei Guifeng, Coker Heather, Rodermund Lisa, Almeida Mafalda, Roach Holly L, Nesterova Tatyana B, Brockdorff Neil
Developmental Epigenetics, Department of Biochemistry, University of Oxford, Oxford, UK.
Centre for Human Genetics, Nuffield Department of Medicine, University of Oxford, Oxford, UK.
Nat Struct Mol Biol. 2025 Sep 9. doi: 10.1038/s41594-025-01663-w.
X-chromosome inactivation (XCI) in mammals is orchestrated by the noncoding RNA X-inactive-specific transcript (Xist) that, together with specific interacting proteins, functions in cis to silence an entire X chromosome. Defined sites on Xist RNA carry the N-methyladenosine (mA) modification and perturbation of the mA writer complex has been found to abrogate Xist-mediated gene silencing. However, the relative contribution of mA and its mechanism of action remain unclear. Here we investigate the role of mA in XCI by applying rapid degron-mediated depletion of METTL3, the catalytic subunit of the mA writer complex, an approach that minimizes indirect effects because of transcriptome-wide depletion of mA. We find that acute loss of METTL3 and mA accelerates Xist-mediated gene silencing and this correlates with increased levels and stability of Xist transcripts. We show that Xist RNA turnover is mediated by the nuclear exosome targeting complex but is independent of the principal nuclear mA reader protein YTHDC1. Our findings demonstrate that the primary function of mA on Xist RNA is to promote Xist RNA turnover, which in turn regulates XCI dynamics.
哺乳动物中的X染色体失活（XCI）由非编码RNA X失活特异性转录本（Xist）精心调控，Xist与特定的相互作用蛋白一起，在顺式作用中使整条X染色体沉默。Xist RNA上的特定位点携带N-甲基腺苷（mA）修饰，并且已发现mA写入复合体的扰动会消除Xist介导的基因沉默。然而，mA的相对贡献及其作用机制仍不清楚。在这里，我们通过应用快速降解介导的mA写入复合体催化亚基METTL3的消耗来研究mA在XCI中的作用，这种方法可将由于转录组范围的mA消耗引起的间接影响降至最低。我们发现METTL3和mA的急性缺失会加速Xist介导的基因沉默，这与Xist转录本水平和稳定性的增加相关。我们表明，Xist RNA周转由核外泌体靶向复合体介导，但独立于主要的核mA读取蛋白YTHDC1。我们的研究结果表明，mA在Xist RNA上的主要功能是促进Xist RNA周转，进而调节XCI动态。
