1. CLIP and cohibin separate rDNA from nucleolar proteins destined for degradation by nucleophagy
- Author
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Takashi Ushimaru, Mitsugu Shimobayashi, Michael N. Hall, Naoki Koike, Md. Golam Mostofa, Shun Hosoyamada, Akter Mst Yeasmin, Nafisa Islam, Muhammad Arifur Rahman, Talukdar Muhammad Waliullah, and Takehiko Kobayashi
- Subjects
0301 basic medicine ,Nucleophagy ,Chromatin Immunoprecipitation ,GENES ,Saccharomyces cerevisiae Proteins ,Cell Survival ,Nucleolus ,PIECEMEAL MICROAUTOPHAGY ,Saccharomyces cerevisiae ,Biology ,DNA, Ribosomal ,Article ,NUCLEUS-VACUOLE JUNCTIONS ,SACCHAROMYCES-CEREVISIAE ,03 medical and health sciences ,chemistry.chemical_compound ,Commentaries ,Protein purification ,Autophagy ,medicine ,Inner membrane ,YEAST ,Spotlight ,Microautophagy ,Ribosomal DNA ,Research Articles ,Science & Technology ,RECEPTOR ,Nuclear Proteins ,Cell Biology ,Cell biology ,Protein Transport ,030104 developmental biology ,medicine.anatomical_structure ,MUTANTS ,chemistry ,CELLS ,Proteolysis ,REPEATS ,AUTOPHAGY ,Life Sciences & Biomedicine ,Nucleus ,Cell Nucleolus ,DNA ,Transcription Factors - Abstract
Nutrient starvation or inactivation of TORC1 induces separation of rDNA and nucleolar proteins in yeast. Mostofa et al. report that the rDNA tethering CLIP–cohibin system repositions nucleolar proteins to sites proximal to the nuclear–vacuolar junction (NVJ), where micronucleophagy occurs, whereas rDNA moves to regions distal to the NVJ., Nutrient starvation or inactivation of target of rapamycin complex 1 (TORC1) in budding yeast induces nucleophagy, a selective autophagy process that preferentially degrades nucleolar components. DNA, including ribosomal DNA (rDNA), is not degraded by nucleophagy, even though rDNA is embedded in the nucleolus. Here, we show that TORC1 inactivation promotes relocalization of nucleolar proteins and rDNA to different sites. Nucleolar proteins move to sites proximal to the nuclear–vacuolar junction (NVJ), where micronucleophagy (or piecemeal microautophagy of the nucleus) occurs, whereas rDNA dissociates from nucleolar proteins and moves to sites distal to NVJs. CLIP and cohibin, which tether rDNA to the inner nuclear membrane, were required for repositioning of nucleolar proteins and rDNA, as well as effective nucleophagic degradation of the nucleolar proteins. Furthermore, micronucleophagy itself was necessary for the repositioning of rDNA and nucleolar proteins. However, rDNA escaped from nucleophagic degradation in CLIP- or cohibin-deficient cells. This study reveals that rDNA–nucleolar protein separation is important for the nucleophagic degradation of nucleolar proteins.
- Published
- 2018
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