scholarly journals Organization of the Pre-autophagosomal Structure Responsible for Autophagosome Formation

2008 ◽  
Vol 19 (5) ◽  
pp. 2039-2050 ◽  
Author(s):  
Tomoko Kawamata ◽  
Yoshiaki Kamada ◽  
Yukiko Kabeya ◽  
Takayuki Sekito ◽  
Yoshinori Ohsumi
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Ternary Complex ◽  
Nutrient Depletion ◽  
Autophagosome Formation ◽  
Yeast Saccharomyces Cerevisiae ◽  
Atg Proteins ◽  
Starvation Condition ◽  
Putative Site ◽  
Starvation Conditions

Autophagy induced by nutrient depletion is involved in survival during starvation conditions. In addition to starvation-induced autophagy, the yeast Saccharomyces cerevisiae also has a constitutive autophagy-like system, the Cvt pathway. Among 31 autophagy-related (Atg) proteins, the function of Atg17, Atg29, and Atg31 is required specifically for autophagy. In this study, we investigated the role of autophagy-specific (i.e., non-Cvt) proteins under autophagy-inducing conditions. For this purpose, we used atg11Δ cells in which the Cvt pathway is abrogated. The autophagy-unique proteins are required for the localization of Atg proteins to the pre-autophagosomal structure (PAS), the putative site for autophagosome formation, under starvation condition. It is likely that these Atg proteins function as a ternary complex, because Atg29 and Atg31 bind to Atg17. The Atg1 kinase complex (Atg1–Atg13) is also essential for recruitment of Atg proteins to the PAS. The assembly of Atg proteins to the PAS is observed only under autophagy-inducing conditions, indicating that this structure is specifically involved in autophagosome formation. Our results suggest that Atg1 complex and the autophagy-unique Atg proteins cooperatively organize the PAS in response to starvation signals.

scholarly journals Atg17 Functions in Cooperation with Atg1 and Atg13 in Yeast Autophagy

2005 ◽  
Vol 16 (5) ◽  
pp. 2544-2553 ◽  
Author(s):  
Yukiko Kabeya ◽  
Yoshiaki Kamada ◽  
Misuzu Baba ◽  
Hirosato Takikawa ◽  
Mitsuru Sasaki ◽  
...  
Keyword(s):  
Kinase Activity ◽  
Biochemical Characterization ◽  
Eukaryotic Cells ◽  
Autophagosome Formation ◽  
Yeast Saccharomyces Cerevisiae ◽  
Starvation Condition ◽  
Mutant Cells ◽  
Two Hybrid ◽  
Starvation Conditions

In eukaryotic cells, nutrient starvation induces the bulk degradation of cellular materials; this process is called autophagy. In the yeast Saccharomyces cerevisiae, most of the ATG (autophagy) genes are involved in not only the process of degradative autophagy, but also a biosynthetic process, the cytoplasm to vacuole (Cvt) pathway. In contrast, the ATG17 gene is required specifically in autophagy. To better understand the function of Atg17, we have performed a biochemical characterization of the Atg17 protein. We found that the atg17Δ mutant under starvation condition was largely impaired in autophagosome formation and only rarely contained small autophagosomes, whose size was less than one-half of normal autophagosomes in diameter. Two-hybrid analyses and coimmunoprecipitation experiments demonstrated that Atg17 physically associates with Atg1-Atg13 complex, and this binding was enhanced under starvation conditions. Atg17-Atg1 binding was not detected in atg13Δ mutant cells, suggesting that Atg17 interacts with Atg1 through Atg13. A point mutant of Atg17, Atg17C24R, showed reduced affinity for Atg13, resulting in impaired Atg1 kinase activity and significant defects in autophagy. Taken together, these results indicate that Atg17-Atg13 complex formation plays an important role in normal autophagosome formation via binding to and activating the Atg1 kinase.

scholarly journals Coupling DNA Replication and Spindle Function in Saccharomyces cerevisiae

Cells ◽  
2021 ◽  
Vol 10 (12) ◽  
pp. 3359
Author(s):  
Dimitris Liakopoulos
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Dna Replication ◽  
Molecular Mechanisms ◽  
Genome Duplication ◽  
Yeast Cells ◽  
Yeast Saccharomyces Cerevisiae ◽  
Spindle Dynamics ◽  
Eukaryotic Organisms ◽  
Spindle Function

In the yeast Saccharomyces cerevisiae DNA replication and spindle assembly can overlap. Therefore, signaling mechanisms modulate spindle dynamics in order to ensure correct timing of chromosome segregation relative to genome duplication, especially when replication is incomplete or the DNA becomes damaged. This review focuses on the molecular mechanisms that coordinate DNA replication and spindle dynamics, as well as on the role of spindle-dependent forces in DNA repair. Understanding the coupling between genome duplication and spindle function in yeast cells can provide important insights into similar processes operating in other eukaryotic organisms, including humans.

The Role of Atg Proteins in Autophagosome Formation

2011 ◽  
Vol 27 (1) ◽  
pp. 107-132 ◽  
Author(s):  
Noboru Mizushima ◽  
Tamotsu Yoshimori ◽  
Yoshinori Ohsumi
Keyword(s):  
Autophagosome Formation ◽  
Atg Proteins

Lipid Rafts in Protein Sorting and Cell Polarity in Budding Yeast Saccharomyces cerevisiae

2002 ◽  
Vol 383 (10) ◽  
pp. 1475-1480 ◽  
Author(s):  
M. Bagnat ◽  
K. Simons
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Cell Surface ◽  
Lipid Rafts ◽  
Cell Polarity ◽  
Budding Yeast ◽  
Protein Sorting ◽  
Yeast Saccharomyces Cerevisiae ◽  
Functional Consequences ◽  
Acyl Chains

Abstract Cellular membranes contain many types and species of lipids. One of the most important functional consequences of this heterogeneity is the existence of microdomains within the plane of the membrane. Sphingolipid acyl chains have the ability of forming tightly packed platforms together with sterols. These platforms or lipid rafts constitute segregation and sorting devices into which proteins specifically associate. In budding yeast, Saccharomyces cerevisiae, lipid rafts serve as sorting platforms for proteins destined to the cell surface. The segregation capacity of rafts also provides the basis for the polarization of proteins at the cell surface during mating. Here we discuss some recent findings that stress the role of lipid rafts as key players in yeast protein sorting and cell polarity.

Multifaceted role of the Saccharomyces cerevisiae Srs2 helicase in homologous recombination regulation

2005 ◽  
Vol 33 (6) ◽  
pp. 1447-1450 ◽  
Author(s):  
M.A. Macris ◽  
P. Sung
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Cell Death ◽  
Dna Replication ◽  
Homologous Recombination ◽  
High Energy ◽  
Yeast Saccharomyces Cerevisiae ◽  
Major Pathway ◽  
Dna Dsbs ◽  
Srs2 Helicase

Homologous recombination (HR) is a major pathway for the elimination of DNA DSBs (double-strand breaks) induced by high-energy radiation and chemicals, or that arise due to endogenous damage and stalled DNA replication forks. If not processed properly, DSBs can lead to cell death, chromosome aberrations and tumorigenesis. Even though HR is important for genome maintenance, it can also interfere with other DNA repair mechanisms and cause gross chromosome rearrangements. In addition, HR can generate DNA or nucleoprotein intermediates that elicit prolonged cell-cycle arrest and sometimes cell death. Genetic analyses in the yeast Saccharomyces cerevisiae have revealed a central role of the Srs2 helicase in preventing untimely HR events and in inhibiting the formation of potentially deleterious DNA structures or nucleoprotein complexes upon DNA replication stress. Paradoxically, efficient repair of DNA DSBs by HR is dependent on Srs2. In this paper, we review recent molecular studies aimed at deciphering the multifaceted role of Srs2 in HR and other cellular processes. These studies have provided critical insights into how HR is regulated in order to preserve genomic integrity and promote cell survival.

scholarly journals Atg27 Is Required for Autophagy-dependent Cycling of Atg9

2007 ◽  
Vol 18 (2) ◽  
pp. 581-593 ◽  
Author(s):  
Wei-Lien Yen ◽  
Julie E. Legakis ◽  
Usha Nair ◽  
Daniel J. Klionsky
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Golgi Complex ◽  
Transmembrane Protein ◽  
Eukaryotic Cells ◽  
Vesicle Formation ◽  
Catabolic Pathway ◽  
Autophagosome Formation ◽  
Yeast Saccharomyces Cerevisiae ◽  
Double Membrane ◽  
Selective Autophagy

Autophagy is a catabolic pathway for the degradation of cytosolic proteins or organelles and is conserved among all eukaryotic cells. The hallmark of autophagy is the formation of double-membrane cytosolic vesicles, termed autophagosomes, which sequester cytoplasm; however, the mechanism of vesicle formation and the membrane source remain unclear. In the yeast Saccharomyces cerevisiae, selective autophagy mediates the delivery of specific cargos to the vacuole, the analog of the mammalian lysosome. The transmembrane protein Atg9 cycles between the mitochondria and the pre-autophagosomal structure, which is the site of autophagosome biogenesis. Atg9 is thought to mediate the delivery of membrane to the forming autophagosome. Here, we characterize a second transmembrane protein Atg27 that is required for specific autophagy in yeast. Atg27 is required for Atg9 cycling and shuttles between the pre-autophagosomal structure, mitochondria, and the Golgi complex. These data support a hypothesis that multiple membrane sources supply the lipids needed for autophagosome formation.

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