National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, P.R. China; College of Life Sciences, University of Chinese Academy of Sciences, Beijing 100049, P.R. China.
National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, P.R. China.
Dev Cell. 2020 Dec 7;55(5):588-602.e7. doi: 10.1016/j.devcel.2020.10.010.
Liquid-liquid phase separation (LLPS) compartmentalizes transcriptional condensates for gene expression, but little is known about how this process is controlled. Here, we showed that depletion of IPMK, encoding inositol polyphosphate multikinase, promotes autophagy and lysosomal function and biogenesis in a TFEB-dependent manner. Cytoplasmic-nuclear trafficking of TFEB, a well-characterized mechanism by which diverse signaling pathways regulate TFEB activity, is not evidently altered by IPMK depletion. We demonstrated that nuclear TFEB forms distinct puncta that colocalize with the Mediator complex and with mRNAs of target lysosomal genes. TFEB undergoes LLPS in vitro. IPMK directly interacts with and inhibits LLPS of TFEB and also dissolves TFEB condensates. Depletion of IPMK increases the number of nuclear TFEB puncta and the co-localization of TFEB with Mediator and mRNAs of target genes. Our study reveals that nuclear-localized IPMK acts as a chaperone to inhibit LLPS of TFEB to negatively control its transcriptional activity.
液-液相分离（LLPS）将转录凝聚物分隔开以进行基因表达，但人们对这一过程如何受到控制知之甚少。在这里，我们表明，肌醇多磷酸激酶（encoding inositol polyphosphate multikinase，IPMK）的耗竭以 TFEB 依赖性的方式促进自噬和溶酶体功能和生物发生。TFEB 的细胞质-核易位是一种众所周知的机制，多种信号通路通过该机制调节 TFEB 活性，但 IPMK 耗竭并未明显改变。我们证明核 TFEB 形成与 Mediator 复合物和靶溶酶体基因的 mRNA 明显共定位的不同点状结构。TFEB 在体外发生液-液相分离。IPMK 直接与 TFEB 的液-液相分离相互作用并抑制其发生，还能溶解 TFEB 凝聚物。IPMK 的耗竭增加了核 TFEB 点状结构的数量以及 TFEB 与 Mediator 和靶基因 mRNA 的共定位。我们的研究揭示了定位于核内的 IPMK 作为一种分子伴侣抑制 TFEB 的液-液相分离，从而负调控其转录活性。
