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rDNA 凝聚促进 rDNA 与核仁蛋白分离,后者在 TORC1 失活后被降解用于核噬作用。

rDNA Condensation Promotes rDNA Separation from Nucleolar Proteins Degraded for Nucleophagy after TORC1 Inactivation.

机构信息

Graduate School of Science and Technology, Shizuoka University, Ohya 836, Suruga-ku, Shizuoka 422-8021, Japan.

Department of Science, Shizuoka University, Ohya 836, Suruga-ku, Shizuoka 422-8021, Japan.

出版信息

Cell Rep. 2019 Sep 24;28(13):3423-3434.e2. doi: 10.1016/j.celrep.2019.08.059.

Abstract

Nutrient starvation and inactivation of target of rapamycin complex 1 (TORC1) protein kinase induce nucleophagy preferentially degrading only nucleolar components in budding yeast. Nucleolar proteins are relocated to sites proximal to the nucleus-vacuole junction (NVJ), where micronucleophagy occurs, whereas rDNA, which is embedded in the nucleolus under normal conditions, moves to NVJ-distal regions, causing rDNA dissociation from nucleolar proteins after TORC1 inactivation. This repositioning is mediated via chromosome linkage INM protein (CLIP)-cohibin complexes that tether rDNA to the inner nuclear membrane. Here, we show that TORC1 inactivation-induced rDNA condensation promotes the repositioning of rDNA and nucleolar proteins. Defects in condensin, Rpd3-Sin3 histone deacetylase (HDAC), and high-mobility group protein 1 (Hmo1), which are involved in TORC1 inactivation-induced rDNA condensation, compromised the repositioning and nucleophagic degradation of nucleolar proteins, although rDNA still escaped from nucleophagic degradation in these mutants. We propose a model in which rDNA condensation after TORC1 inactivation generates a motive force for the repositioning of rDNA and nucleolar proteins.

摘要

营养饥饿和雷帕霉素靶蛋白复合物 1(TORC1)蛋白激酶失活诱导核噬作用,优先降解酿酒酵母中仅核仁成分。核仁蛋白被重定位到靠近核-液泡连接点(NVJ)的位置,在这里发生微核噬作用,而正常情况下嵌入核仁中的 rDNA 则移动到 NVJ 远端区域,导致 TORC1 失活后 rDNA 与核仁蛋白解离。这种重定位是通过染色体连接内膜蛋白(CLIP)-cohibin 复合物介导的,该复合物将 rDNA 固定在内核膜上。在这里,我们表明 TORC1 失活诱导的 rDNA 凝聚促进了 rDNA 和核仁蛋白的重定位。参与 TORC1 失活诱导的 rDNA 凝聚的 condensin、Rpd3-Sin3 组蛋白去乙酰化酶(HDAC)和高迁移率族蛋白 1(Hmo1)的缺陷,破坏了核仁蛋白的重定位和核噬作用降解,尽管在这些突变体中 rDNA 仍逃避核噬作用降解。我们提出了一个模型,即在 TORC1 失活后 rDNA 凝聚产生了 rDNA 和核仁蛋白重定位的动力。

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