scholarly journals CLIP and cohibin separate rDNA from nucleolar proteins destined for degradation by nucleophagy

2018 ◽  
Vol 217 (8) ◽  
pp. 2675-2690 ◽  
Author(s):  
Md. Golam Mostofa ◽  
Muhammad Arifur Rahman ◽  
Naoki Koike ◽  
Akter MST Yeasmin ◽  
Nafisa Islam ◽  
...  
Keyword(s):  
Ribosomal Dna ◽  
Nuclear Membrane ◽  
Protein Separation ◽  
Budding Yeast ◽  
Nutrient Starvation ◽  
Nucleolar Protein ◽  
Target Of Rapamycin ◽  
Selective Autophagy ◽  
Nucleolar Proteins ◽  
Nucleolar Components

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.

scholarly journals Sorting the trash: Micronucleophagy gets selective

2018 ◽  
Vol 217 (8) ◽  
pp. 2605-2607
Author(s):  
Pauline Verlhac ◽  
Fulvio Reggiori
Keyword(s):  
Cell Survival ◽  
Ribosomal Dna ◽  
Nucleolar Proteins ◽  
Cell Biol ◽  
Autophagic Degradation ◽  
Nucleolar Components

During micronucleophagy, the nucleolus is targeted by autophagic degradation, but although nucleolar proteins are recycled, ribosomal DNA is spared. Mostofa et al. (2018. J. Cell Biol. https://doi.org/10.1083/jcb.201706164) reveal that the separation of these two nucleolar components is mediated by the CLIP and cohibin complexes and is vital for cell survival during starvation.

scholarly journals Mutations in nucleolar proteins lead to nucleolar accumulation of polyA+ RNA in Saccharomyces cerevisiae.

1995 ◽  
Vol 6 (9) ◽  
pp. 1103-1110 ◽  
Author(s):  
T Kadowaki ◽  
R Schneiter ◽  
M Hitomi ◽  
A M Tartakoff
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Rna Polymerase ◽  
Rna Polymerase I ◽  
Nucleolar Protein ◽  
Rrna Synthesis ◽  
Ribosomal Subunits ◽  
Nucleolar Proteins ◽  
Synthesis And Processing ◽  
Polymerase I ◽  
Nucleolar Components

Synthesis of mRNA and rRNA occur in the chromatin-rich nucleoplasm and the nucleolus, respectively. Nevertheless, we here report that a Saccharomyces cerevisiae gene, MTR3, previously implicated in mRNA transport, codes for a novel essential 28-kDa nucleolar protein. Moreover, in mtr3-1 the accumulated polyA+ RNA actually colocalizes with nucleolar antigens, the nucleolus becomes somewhat disorganized, and rRNA synthesis and processing are inhibited. A strain with a ts conditional mutation in RNA polymerase I also shows nucleolar accumulation of polyA+ RNA, whereas strains with mutations in the nucleolar protein Nop1p do not. Thus, in several mutant backgrounds, when mRNA cannot be exported i concentrates in the nucleolus. mRNA may normally encounter nucleolar components before export and proteins such as Mtr3p may be critical for export of both mRNA and ribosomal subunits.

scholarly journals Identification of a novel nucleolar protein complex required for mitotic chromosome segregation through centromeric accumulation of Aurora B

2020 ◽  
Vol 48 (12) ◽  
pp. 6583-6596
Author(s):  
Akiko Fujimura ◽  
Yuki Hayashi ◽  
Kazashi Kato ◽  
Yuichiro Kogure ◽  
Mutsuro Kameyama ◽  
...  
Keyword(s):  
Chromosome Segregation ◽  
Protein Complex ◽  
Metaphase Plate ◽  
Nucleolar Protein ◽  
Aurora B ◽  
Mitotic Progression ◽  
Mitotic Chromosomes ◽  
Nucleolar Proteins ◽  
Chromatid Cohesion ◽  
Wd Repeat

Abstract The nucleolus is a membrane-less nuclear structure that disassembles when cells undergo mitosis. During mitosis, nucleolar factors are thus released from the nucleolus and dynamically change their subcellular localization; however, their functions remain largely uncharacterised. Here, we found that a nucleolar factor called nucleolar protein 11 (NOL11) forms a protein complex with two tryptophan-aspartic acid (WD) repeat proteins named WD-repeat protein 43 (WDR43) and Cirhin in mitotic cells. This complex, referred to here as the NWC (NOL11-WDR43-Cirhin) complex, exists in nucleoli during interphase and translocates to the periphery of mitotic chromosomes, i.e., perichromosomal regions. During mitotic progression, both the congression of chromosomes to the metaphase plate and sister chromatid cohesion are impaired in the absence of the NWC complex, as it is required for the centromeric enrichment of Aurora B and the associating phosphorylation of histone H3 at threonine 3. These results reveal the characteristics of a novel protein complex consisting of nucleolar proteins, which is required for regulating kinetochores and centromeres to ensure faithful chromosome segregation.

scholarly journals PP2C phosphatases promote autophagy by dephosphorylation of the Atg1 complex

2019 ◽  
Vol 116 (5) ◽  
pp. 1613-1620 ◽  
Author(s):  
Gonen Memisoglu ◽  
Vinay V. Eapen ◽  
Ying Yang ◽  
Daniel J. Klionsky ◽  
James E. Haber
Keyword(s):  
Kinase Activity ◽  
Budding Yeast ◽  
Nutrient Starvation ◽  
Phosphorylation Sites ◽  
Phagophore Assembly Site ◽  
Assembly Site

Macroautophagy is orchestrated by the Atg1-Atg13 complex in budding yeast. Under nutrient-rich conditions, Atg13 is maintained in a hyperphosphorylated state by the TORC1 kinase. After nutrient starvation, Atg13 is dephosphorylated, triggering Atg1 kinase activity and macroautophagy induction. The phosphatases that dephosphorylate Atg13 remain uncharacterized. Here, we show that two redundant PP2C phosphatases, Ptc2 and Ptc3, regulate macroautophagy by dephosphorylating Atg13 and Atg1. In the absence of these phosphatases, starvation-induced macroautophagy and the cytoplasm-to-vacuole targeting pathway are inhibited, and the recruitment of the essential autophagy machinery to the phagophore assembly site is impaired. Expressing a genomic ATG13-8SA allele lacking key TORC1 phosphorylation sites partially bypasses the macroautophagy defect in ptc2Δ ptc3Δ strains. Moreover, Ptc2 and Ptc3 interact with the Atg1-Atg13 complex. Taken together, these results suggest that PP2C-type phosphatases promote macroautophagy by regulating the Atg1 complex.

scholarly journals Spindle-independent condensation-mediated segregation of yeast ribosomal DNA in late anaphase

2005 ◽  
Vol 168 (2) ◽  
pp. 209-219 ◽  
Author(s):  
Félix Machín ◽  
Jordi Torres-Rosell ◽  
Adam Jarmuz ◽  
Luis Aragón
Keyword(s):  
Cell Division ◽  
Ribosomal Dna ◽  
Budding Yeast ◽  
Mitotic Cell ◽  
Yeast Genome ◽  
Daughter Cells ◽  
Late Anaphase ◽  
Mother And Daughter ◽  
The Right ◽  
Chromosome Resolution

Mitotic cell division involves the equal segregation of all chromosomes during anaphase. The presence of ribosomal DNA (rDNA) repeats on the right arm of chromosome XII makes it the longest in the budding yeast genome. Previously, we identified a stage during yeast anaphase when rDNA is stretched across the mother and daughter cells. Here, we show that resolution of sister rDNAs is achieved by unzipping of the locus from its centromere-proximal to centromere-distal regions. We then demonstrate that during this stretched stage sister rDNA arrays are neither compacted nor segregated despite being largely resolved from each other. Surprisingly, we find that rDNA segregation after this period no longer requires spindles but instead involves Cdc14-dependent rDNA axial compaction. These results demonstrate that chromosome resolution is not simply a consequence of compacting chromosome arms and that overall rDNA compaction is necessary to mediate the segregation of the long arm of chromosome XII.

scholarly journals Multiple Orientation-Dependent, Synergistically Interacting, Similar Domains in the Ribosomal DNA Replication Origin of the Fission Yeast, Schizosaccharomyces pombe

1998 ◽  
Vol 18 (12) ◽  
pp. 7294-7303 ◽  
Author(s):  
Soo-Mi Kim ◽  
Joel A. Huberman
Keyword(s):  
Dna Replication ◽  
Schizosaccharomyces Pombe ◽  
Fission Yeast ◽  
Ribosomal Dna ◽  
Replication Origin ◽  
Budding Yeast ◽  
Sequence Motifs ◽  
Dna Replication Origin ◽  
Dna Replication Origins ◽  
Origin Function

ABSTRACT Previous investigations have shown that the fission yeast,Schizosaccharomyces pombe, has DNA replication origins (500 to 1500 bp) that are larger than those in the budding yeast,Saccharomyces cerevisiae (100 to 150 bp). Deletion and linker substitution analyses of two fission yeast origins revealed that they contain multiple important regions with AT-rich asymmetric (abundant A residues in one strand and T residues in the complementary strand) sequence motifs. In this work we present the characterization of a third fission yeast replication origin, ars3001, which is relatively small (∼570 bp) and responsible for replication of ribosomal DNA. Like previously studied fission yeast origins,ars3001 contains multiple important regions. The three most important of these regions resemble each other in several ways: each region is essential for origin function and is at least partially orientation dependent, each region contains similar clusters of A+T-rich asymmetric sequences, and the regions can partially substitute for each other. These observations suggest that ars3001function requires synergistic interactions between domains binding similar proteins. It is likely that this requirement extends to other fission yeast origins, explaining why such origins are larger than those of budding yeast.

scholarly journals The Budding Yeast Homolog of the Human EBNA1-binding Protein 2 (Ebp2p) Is an Essential Nucleolar Protein Required for Pre-rRNA Processing

2000 ◽  
Vol 275 (37) ◽  
pp. 28764-28773 ◽  
Author(s):  
Michael D. Huber ◽  
Jessica H. Dworet ◽  
Kathy Shire ◽  
Lori Frappier ◽  
Michael A. McAlear
Keyword(s):  
Budding Yeast ◽  
Binding Protein ◽  
Nucleolar Protein ◽  
Rrna Processing ◽  
Yeast Homolog

scholarly journals Yeast Nuclear Envelope Subdomains with Distinct Abilities to Resist Membrane Expansion

2006 ◽  
Vol 17 (4) ◽  
pp. 1768-1778 ◽  
Author(s):  
Joseph L. Campbell ◽  
Alexander Lorenz ◽  
Keren L. Witkin ◽  
Thomas Hays ◽  
Josef Loidl ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Endoplasmic Reticulum ◽  
Nuclear Envelope ◽  
Nuclear Membrane ◽  
Budding Yeast ◽  
Phospholipid Biosynthesis ◽  
Yeast Saccharomyces Cerevisiae ◽  
Nuclear Compartment ◽  
Round Shape ◽  
Nuclear Protrusion

Little is known about what dictates the round shape of the yeast Saccharomyces cerevisiae nucleus. In spo7Δ mutants, the nucleus is misshapen, exhibiting a single protrusion. The Spo7 protein is part of a phosphatase complex that represses phospholipid biosynthesis. Here, we report that the nuclear protrusion of spo7Δ mutants colocalizes with the nucleolus, whereas the nuclear compartment containing the bulk of the DNA is unaffected. Using strains in which the nucleolus is not intimately associated with the nuclear envelope, we show that the single nuclear protrusion of spo7Δ mutants is not a result of nucleolar expansion, but rather a property of the nuclear membrane. We found that in spo7Δ mutants the peripheral endoplasmic reticulum (ER) membrane was also expanded. Because the nuclear membrane and the ER are contiguous, this finding indicates that in spo7Δ mutants all ER membranes, with the exception of the membrane surrounding the bulk of the DNA, undergo expansion. Our results suggest that the nuclear envelope has distinct domains that differ in their ability to resist membrane expansion in response to increased phospholipid biosynthesis. We further propose that in budding yeast there is a mechanism, or structure, that restricts nuclear membrane expansion around the bulk of the DNA.

scholarly journals Genomic Instability and Cellular Senescence: Lessons From the Budding Yeast

2021 ◽  
Vol 8 ◽  
Author(s):  
Jee Whu Lee ◽  
Eugene Boon Beng Ong
Keyword(s):  
Ribosomal Dna ◽  
Cellular Senescence ◽  
Molecular Mechanisms ◽  
Budding Yeast ◽  
Genetic Alterations ◽  
Lessons Learned ◽  
Complex Biological Process ◽  
Dna Instability ◽  
Permanent Cell ◽  
Living Organisms

Aging is a complex biological process that occurs in all living organisms. Aging is initiated by the gradual accumulation of biomolecular damage in cells leading to the loss of cellular function and ultimately death. Cellular senescence is one such pathway that leads to aging. The accumulation of nucleic acid damage and genetic alterations that activate permanent cell-cycle arrest triggers the process of senescence. Cellular senescence can result from telomere erosion and ribosomal DNA instability. In this review, we summarize the molecular mechanisms of telomere length homeostasis and ribosomal DNA stability, and describe how these mechanisms are linked to cellular senescence and longevity through lessons learned from budding yeast.

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