Research, Research Articles
Single telomere length analysis in Ustilago maydis, a high-resolution tool for examining fungal telomere length distribution and C-strand 5’-end processing
Ganduri Swapna1, Eun Young Yu1 and Neal F. Lue1, 2
This article introduces the development of single telomere length analysis (STELA) for Ustilago maydis, a basidiomycete fungus, enabling the precise measurement of telomere lengths and distributions. The study demonstrates STELA's utility in revealing the existence of relatively short telomeres in wild-type cells, preferential loss of long telomeres in a mutant defective in telomere replication, and the characterization of telomere C-strand 5’ ends, highlighting U. maydis as a strong model for telomere research.
Temporal analysis of the autophagic and apoptotic phenotypes in Leishmania parasites
Louise Basmaciyan1, Laurence Berry2, Julie Gros3, Nadine Azas3 and Magali Casanova3
This article details a comprehensive analysis of miltefosine-induced cell death and autophagy in Leishmania major, providing criteria for clear identification of apoptotic and autophagic cells, demonstrating the sequential nature of autophagy followed by apoptosis in nutrient-deprived conditions, and cautioning against using the generic kinase inhibitor staurosporine as a Leishmania apoptosis inducer, with the aim of improving the understanding of these processes and their targeting for new anti-leishmanial drugs.
Snf1 cooperates with the CWI MAPK pathway to mediate the degradation of Med13 following oxidative stress
Stephen D. Willis1, David C. Stieg1, Kai Li Ong2, Ravina Shah1,3, Alexandra K. Strich1,4, Julianne H. Grose2 and Katrina F. Cooper1
This article explores the response of eukaryotic cells to environmental stress, highlighting the role of the conserved cyclin C-Cdk8 kinase in determining pro-survival or pro-death programs. Specifically, it discusses how oxidative stress triggers the destruction of Med13 by the SCFGrr1 ubiquitin ligase, releasing cyclin C to promote mitochondrial fission and cell death in Saccharomyces cerevisiae. Additionally, it reveals that the AMP kinase Snf1 activates a separate degron in Med13, contributing to the complex regulation of Med13 degradation following H2O2 stress through the coordination of the cell wall integrity and MAPK pathways.
Importance of polyphosphate in the Leishmania life cycle
Kid Kohl1, Haroun Zangger1, Matteo Rossi1, Nathalie Isorce1, Lon-Fye Lye2, Katherine L. Owens2, Stephen M. Beverley2, Andreas Mayer1 and Nicolas Fasel1
This article explores the importance of polyphosphate (polyP) in Leishmania parasites, emphasizing the role of the polyP polymerase VTC4 and its impact on parasite survival at higher temperatures. Additionally, it discusses the effects of VTC4 knockout in mouse infections, noting a delay in lesion formation and strong pathology in L. major VTC4 knockout, without confirmation through complementation and no alteration in L. guyanensis infections in mice with VTC4 knockdown.
Antagonism between salicylate and the cAMP signal controls yeast cell survival and growth recovery from quiescence
Maurizio D. Baroni1, Sonia Colombo2 and Enzo Martegani2
This article describes the effects of salicylate, the main metabolite of aspirin, on S. cerevisiae cells. It outlines how salicylate influences glucose transport, sugar phosphate biosynthesis, and apoptosis, particularly in MnSOD-deficient cells. Furthermore, it emphasizes the significant impact of salicylate on the exit from a quiescent state, inhibiting growth recovery and viability in long-term stationary phase cells. The passage also discusses the potential therapeutic implications of understanding the antagonistic relationship between cAMP and salicylate in targeting quiescent cancer cells with stem-like properties.
Evolution of substrate specificity in the Nucleobase-Ascorbate Transporter (NAT) protein family
Anezia Kourkoulou1,#, Alexandros A. Pittis2,# and George Diallinas1
L-ascorbic acid (vitamin C) is an essential metabolite in animals and plants due to its role as an enzyme co-factor and antioxidant activity. Here, Kourkoulou et al. show further evidence that ascorbate-specific Nucleobase-Ascorbate Transporters (NATs) evolved by optimization of a sub-function of ancestral nucleobase transporters.
Valine biosynthesis in Saccharomyces cerevisiae is regulated by the mitochondrial branched-chain amino acid aminotransferase Bat1
Natthaporn Takpho1, Daisuke Watanabe1 and Hiroshi Takagi1
In Saccharomyces cerevisiae, the yeast, the Bat1 and Bat2 proteins, which are branched-chain amino acid aminotransferases, play distinct roles in valine biosynthesis and cell growth regulation, with Bat1 primarily located in the mitochondria and Bat2 in the cytosol, and the mitochondria being identified as the major site of valine biosynthesis in this yeast.
Microbial competition between Escherichia coli and Candida albicans reveals a soluble fungicidal factor
Damien J. Cabral1, Swathi Penumutchu1, Colby Norris1,2, Jose Ruben Morones-Ramirez3,4 and Peter Belenky1
Localized and systemic fungal infections caused by Candida albicans can lead to significant mortality and morbidity. Here, Cabral et al. show that E. coli produces a soluble factor that kills C. albicans in a magnesium-dependent fashion such that depletion of available magnesium is essential for toxicity.
Spontaneous mutations in CYC8 and MIG1 suppress the short chronological lifespan of budding yeast lacking SNF1/AMPK
Nazif Maqani1,#, Ryan D. Fine1,#, Mehreen Shahid1, Mingguang Li1,2, Elisa Enriquez-Hesles1 and Jeffrey S. Smith1
Chronologically aging yeast cells are prone to adaptive regrowth, whereby mutants with a survival advantage spontaneously appear and re-enter the cell cycle in stationary phase cultures. Here, Magani et al. identified specific downstream SNF1 targets responsible for CLS extension during CR.
Impact of histone H4K16 acetylation on the meiotic recombination checkpoint in Saccharomyces cerevisiae
December 4, 2016
In meiotic cells, the pachytene checkpoint or meiotic recombination checkpoint is a surveillance mechanism that monitors critical processes, such as recombination and chromosome synapsis, which are essential for proper distribution of chromosomes to the meiotic progeny. We report here that Sas2-mediated acetylation of histone H4 at lysine 16 (H4K16ac) modulates meiotic checkpoint activity in response to synaptonemal complex defects. Our results reveal that proper levels of H4K16ac orchestrate this meiotic quality control mechanism and that Sir2 impinges on additional targets to fully activate the checkpoint.
The ubiquitin-conjugating enzyme, Ubc1, indirectly regulates SNF1 kinase activity via Forkhead-dependent transcription
November 5, 2016
The SNF1 kinase class of serine/threonine kinases, which includes the AMP-dependent protein kinase (AMPK) in other systems, are of widespread interest because of their important roles in glucose homeostasis, stress resistance, and aging. Our goal was to identify discrete ubiquitin-conjugating enzymes that are involved in SNF1 kinase activity in response to glucose levels and anticipated revealing those which are involved in Snf1-Ub attachment. Here, we report that the cell cycle and stress-related E2, Ubc1, indirectly affects SNF1 kinase activity not through stability, but through upstream events.
Phylogenetic profiles of all membrane transport proteins of the malaria parasite highlight new drug targets
August 30, 2016
In order to combat the on-going malaria epidemic, discovery of new drug targets remains vital. Proteins that are essential to survival and specific to malaria parasites are key candidates. Here, we present a comprehensive orthology assignment of all Plasmodium falciparum putative membrane transport proteins and provide a detailed overview of the associated essential gene functions obtained through experimental genetics studies in human and murine model parasites.
VDAC regulates AAC-mediated apoptosis and cytochrome c release in yeast
August 25, 2016
Mitochondrial outer membrane permeabilization is a key event in apoptosis processes leading to the release of lethal factors. In this study, we sought to determine whether Por1p functionally interacts with ADP/ATP carrier (AAC) proteins, as well as its contribution to cytochrome c release and yeast apoptosis induced by acetic acid treatment. Our data indicate that Por1p may regulate cell survival by acting as a negative regulator of AAC proteins in the apoptotic cascade.
Attenuation of polyglutamine-induced toxicity by enhancement of mitochondrial OXPHOS in yeast and fly models of aging
July 26, 2016
Defects in mitochondrial biogenesis and function are common in many neurodegenerative disorders, including Huntington’s disease (HD). We could shown that enhancement of mitochondrial biogenesis protects against neurodegeneration in HD yeast and fly models. Our results suggest that therapeutic interventions aiming at the enhancement of mitochondrial respiration and OXPHOS could reduce polyQ toxicity and delay disease onset.
Cox1 mutation abrogates need for Cox23 in cytochrome c oxidase biogenesis
June 30, 2016
Cox23 is a known conserved assembly factor for cytochrome c oxidase, although its role in cytochrome c oxidase (CcO) biogenesis remains unresolved. To gain additional insights into its role, we isolated spontaneous suppressors of the respiratory growth defect in cox23∆ yeast cells. In this report, we describe the isolation of a robust suppressor of the respiratory defect in cox23∆ cells that mapped to the mitochondrial-encoded Cox1 subunit.
Construction and evaluation of yeast expression networks by database-guided predictions
May 10, 2016
DNA-Microarrays are powerful tools to obtain expression data on the genome-wide scale. We set out to define a way to cluster microarray data according to their expressional relationship and to obtain information on the significance of this clustering approach.
Optogenetic monitoring identifies phosphatidylthreonine-regulated calcium homeostasis in Toxoplasma gondii
May 1, 2016
Toxoplasma gondii is an obligate intracellular parasite, which inflicts acute as well as chronic infections in a wide range of warm-blooded vertebrates. Using an optogenetic sensor to monitor subcellular calcium in this model intracellular pathogen we found a novel regulatory function of phosphatidylthreonine in calcium signaling.
Formaldehyde fixation is detrimental to actin cables in glucose-depleted S. cerevisiae cells
April 13, 2016
Actin filaments form cortical patches and emanating cables in fermenting cells of Saccharomyces cerevisiae. We assume that stability of actin cables reflects the metabolic status of the cell. Based on comparison of live and formaldehyde-fixed cells, our data suggest that formaldehyde affects respiration before fixation and this uneven signaling results in destabilization of actin cables in glucose-deprived cells.
Insights into dynamin-associated disorders through analysis of equivalent mutations in the yeast dynamin Vps1
March 22, 2016
The dynamins represent a superfamily of proteins that have been shown to function in a wide range of membrane fusion and fission events. An increasing number of mutations in the human classical dynamins, Dyn-1 and Dyn-2 has been reported, with diseases caused by these changes ranging from Charcot-Marie-Tooth disorder to epileptic encephalopathies. This study aimed to use the dynamin-like protein Vps1 of Saccharomyces cerevisiae as a model to gain insights into the mechanistic defects caused by specific dynamin mutations considered to underlie a number of diseases.