Overexpression of autophagy-related genes inhibits yeast filamentous growth (original) (raw)
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An Interrelationship Between Autophagy and Filamentous Growth in Budding Yeast
Genetics, 2007
Over the last 15 years, yeast pseudohyphal growth (PHG) has been the focus of intense research interest as a model of fungal pathogenicity. Specifically, PHG is a stress response wherein yeast cells deprived of nitrogen form filaments of elongated cells. Nitrogen limitation also induces autophagy, a ubiquitous eukaryotic stress response in which proteins are trafficked to the vacuole/lysosome for degradation and recycling. Although autophagy and filamentous growth are both responsive to nitrogen stress, a link between these processes has not been investigated to date. Here, we present several studies describing an interrelationship between autophagy and filamentous growth. By microarray-based expression profiling, we detect extensive upregulation of the pathway governing autophagy during early PHG and find both processes active under conditions of nitrogen stress in a filamentous strain of budding yeast. Inhibition of autophagy results in increased PHG, and autophagy-deficient yeast induce PHG at higher concentrations of available nitrogen. Our results suggest a model in which autophagy mitigates nutrient stress, delaying the onset of PHG; conversely, inhibition of autophagy exacerbates nitrogen stress, resulting in precocious and overactive PHG. This physiological connection highlights the central role of autophagy in regulating the cell's nutritional state and the responsiveness of PHG to that state.
Cells, 2012
The budding yeast Saccharomyces cerevisiae responds to nutritional stress through the regulated activities of signaling pathways mediating autophagy and other conserved cellular processes. Autophagy has been studied intensely in yeast, where over 30 autophagy-related genes have been identified with defined roles enabling the formation of autophagic vesicles and their subsequent trafficking to the central yeast vacuole. Much less, however, is known regarding the regulatory mechanisms through which autophagy is integrated with other yeast stress responses. Nitrogen limitation initiates autophagy and pseudohyphal growth in yeast, the latter being a fascinating stress response characterized by the formation of multicellular chains or filaments of elongated cells. An increasing body of evidence suggests an interrelationship between processes responsive to nitrogen stress with cAMP-dependent PKA and the TOR kinase complex acting as key regulators of autophagy, pseudohyphal growth, and end...
BMC Research Notes, 2019
Objective: A classical method to quantitatively determine the starvation sensitivity phenotype of autophagy mutant budding yeast strains is to starve them for a period of time and then to assess the proportion of cells that retain the ability to form colonies when the availability of nutrients is restored. The readout of this colony-formation assay is generally evaluated after a fixed period of time following the restoration of nutrients, so that it can be considered an endpoint assay. One drawback we have identified is the inability to characterize subtle intermediary phenotypes that are detectable at the molecular level but fail to reach statistical significance in the colony formation experiment. We set out to determine whether a more dynamic measurement of growth during recovery after starvation would increase the sensitivity with which we are able to detect partial loss-of-function phenotypes. Results: We describe a 96-well plate-based assay to kinetically assess starvation sensitivity in budding yeast that allows for the quantitative detection of very modest starvation sensitivity phenotypes with statistical significance in autophagy mutant yeast strains lacking the ATG27 gene.
Microbiology, 2009
Autophagy is triggered when organisms sense radical environmental changes, including nutritional starvation. During autophagy, cytoplasmic components, including organelles, are enclosed within autophagosomes and are degraded upon lysosome–vacuole fusion. In this study, we show that processing of GFP-tagged Atg8 can serve as a marker for autophagy in the fission yeastSchizosaccharomyces pombe. Using this marker, 13 Atg homologues were also found to be required for autophagy in fission yeast. In budding yeast, autophagy-deficient mutants are known to be sterile, whereas in fission yeast we found that up to 30 % of autophagy-defective cells with amino acid auxotrophy were able to recover sporulation when an excess of required amino acids was supplied. Furthermore, we found that approximately 15 % of the autophagy-defective cells were also able to sporulate when a prototrophic strain was subjected to nitrogen starvation, which suggested that fission yeast may store sufficient intracellu...
Autophagy: mechanism and physiological relevance'brewed'from yeast studies
2012
Autophagy is a highly conserved process of quality control occurring inside cells by which cytoplasmic material can be degraded and the products recycled for use as new building blocks or for energy production. The rapid progress and 'explosion' of knowledge concerning autophagic processes in mammals/humans that has occurred over the last 15 years was driven by fundamental studies in yeast, principally using Saccharomyces cerevisiae, leading to the identification and cloning of genes required for autophagy. This chapter reviews the role of yeast studies in understanding the molecular mechanisms of autophagic processes, focusing on aspects that are conserved in mammals/humans and how autophagy is increasingly implicated in the pathogenesis of disease and is required for development and differentiation.
Aging Cell, 2009
Following cessation of growth, yeast cells remain viable in a nondividing state for a period of time known as the chronological lifespan (CLS). Autophagy is a degradative process responsible for amino acid recycling in response to nitrogen starvation and amino acid limitation. We have investigated the role of autophagy during chronological aging of yeast grown in glucose minimal media containing different supplemental essential and nonessential amino acids. Deletion of ATG1 or ATG7, both of which are required for autophagy, reduced CLS, whereas deletion of ATG11, which is required for selective targeting of cellular components to the vacuole for degradation, did not reduce CLS. The nonessential amino acids isoleucine and valine, and the essential amino acid leucine, extended CLS in autophagy-deficient as well as autophagy-competent yeast. This extension was suppressed by constitutive expression of GCN4, which encodes a transcriptional regulator of general amino acid control (GAAC). Consistent with this, GCN4 expression was reduced by isoleucine and valine. Furthermore, elimination of the leucine requirement extended CLS and prevented the effects of constitutive expression of GCN4. Interestingly, deletion of LEU3, a GAAC target gene encoding a transcriptional regulator of branched side chain amino acid synthesis, dramatically increased CLS in the absence of amino acid supplements. In general, this indicates that activation of GAAC reduces CLS whereas suppression of GAAC extends CLS in minimal medium. These findings demonstrate important roles for autophagy and amino acid homeostasis in determining CLS in yeast.
Autophagy in the fission yeastSchizosaccharomyces pombe
FEBS Letters, 2009
Autophagy is a non-selective degradation process in eukaryotic cells. The genome sequence of the fission yeast Schizosaccharomyces pombe has revealed that many of the genes required for autophagy are common between the fission yeast and budding yeast, suggesting that the basic machinery of autophagy is conserved between these species. Autophagy in fission yeast is specifically induced by nitrogen starvation based on monitoring a GFP-Atg8p marker. Upon nitrogen starvation, fission yeast cells exit the vegetative cell cycle and initiate sexual differentiation to produce spores. Most of the nitrogen used for de novo protein synthesis during sporulation derives from the autophagic protein degradation system. This review focuses on the recent advances in the role of autophagy in fission yeast.
2020
F-box motif encoding YDR131C is functionally uncharacterized gene which forms the complex with the SCF-E3 ligase. The F-box motif containing proteins are involved in substrate recruitment for the ubiquitination and subsequent degradation through 26S proteasome. Autophagy gene, ATG1 (ULK1in human) is a well conserved serine-threonine kinase, required for vesicle formation and cytoplasm to vacuole targeting pathway. Atg1p forms the complex with Atg13p and Atg17p during autophagy. The understanding of crosstalk between ubiquitin and autophagy pathways is crucial for synthetic lethality screen and drug targeting. Here we have conducted the study for genetic interaction between uncharacterized YDR131C and ATG1 gene representing both specific and non-specific protein degradation pathways. The single and double gene knockout strains of YDR131Cand ATG1 genes were constructed in the BY4741 genetic background and analysed for growth fitness. The strains were also evaluated for cellular growth Manjithya, JNCASR, Dr.