The 5'-3' exoribonuclease Xrn2, known as Rat1 in yeasts, terminates mRNA transcription by RNA polymerase II (RNAPII). In the torpedo model of termination, the activity of Xrn2/Rat1 is enhanced by Rai1, which is recruited to the termination site by Rtt103, an adaptor protein binding to the RNAPII C-terminal domain (CTD). The overall architecture of the Xrn2/Rat1-Rai1-Rtt103 complex remains unknown. We combined structural biology methods to characterize the torpedo complex from Saccharomyces cerevisiae and Chaetomium thermophilum. Comparison of the structures from these organisms revealed a conserved protein core fold of the subunits, but significant variability in their interaction interfaces. We found that in the mesophile, Rtt103 utilizes an unstructured region to augment a Rai1 β-sheet, while in the thermophile Rtt103 binds to a C-terminal helix of Rai1 via its CTD-interacting domain with an α-helical fold. These different torpedo complex assemblies reflect adaptations to the environment and impact complex recruitment to RNAPII.

• Klíčová slova
• NMR, RNAPII, cryo-EM, exonuclease, structure, termination, thermophiles, torpedo complex,
• MeSH
• Chaetomium * metabolismus   chemie   MeSH
• exoribonukleasy * chemie   metabolismus   genetika   MeSH
• krystalografie rentgenová MeSH
• molekulární modely MeSH
• RNA-polymerasa II metabolismus   chemie   MeSH
• Saccharomyces cerevisiae - proteiny * chemie   metabolismus   genetika   MeSH
• Saccharomyces cerevisiae * metabolismus   chemie   MeSH
• vazba proteinů MeSH
• vazebná místa MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• exoribonukleasy * MeSH
• RAT1 protein, S cerevisiae MeSH Prohlížeč
• RNA-polymerasa II MeSH
• Saccharomyces cerevisiae - proteiny * MeSH

Sterols perform essential structural and signalling functions in living organisms. Ergosterol contributes to the fluidity, permeability, microdomain formation and functionality of proteins in the yeast membrane. In our study, desmosterol was the most successful at compensating for the lack of ergosterol in Saccharomyces cerevisiae, besides stigmasterol and sitosterol. These three sterols supported cell growth without causing severe morphological defects, unlike cholesterol, 7-dehydrocholesterol, lathosterol, cholestanol or lanosterol. Together with ergosterol, they were also able to bring the plasma membrane potential of hem1Δ cells closer to the level of the wild type. In addition, desmosterol conferred even higher thermotolerance to yeast than ergosterol. Some sterols counteracted the antifungal toxicity of polyenes, azoles and terbinafine to hem1Δ cells. Plant sterols (stigmasterol, sitosterol) and desmosterol ensured the glucose-induced activation of H+-ATPase in hem1Δ cells analogously to ergosterol, whereas cholesterol and 7-dehydrocholesterol were less effective. Exogenous ergosterol, stigmasterol, sitosterol, desmosterol and cholesterol also improved the growth of Candida glabrata and Candida albicans in the presence of inhibitory concentration of fluconazole. The proper incorporation of exogenous sterols into the membrane with minimal adverse side effects on membrane functions was mainly influenced by the structure of the sterol acyl chain, and less by their ring structures.

• Klíčová slova
• Ergosterol, H(+)-ATPase, Multidrug resistance, Plasma membrane, Yeast, diS-C(3)(3) assay,
• MeSH
• antifungální látky * farmakologie   MeSH
• buněčná membrána * účinky léků   metabolismus   fyziologie   MeSH
• desmosterol metabolismus   farmakologie   MeSH
• ergosterol * metabolismus   farmakologie   MeSH
• fungální léková rezistence * MeSH
• mikrobiální testy citlivosti MeSH
• protonové ATPasy * metabolismus   MeSH
• Saccharomyces cerevisiae - proteiny metabolismus   genetika   MeSH
• Saccharomyces cerevisiae * účinky léků   enzymologie   fyziologie   metabolismus   MeSH
• sitosteroly metabolismus   farmakologie   MeSH
• steroly * metabolismus   farmakologie   MeSH
• stigmasterol metabolismus   farmakologie   MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• antifungální látky * MeSH
• desmosterol MeSH
• ergosterol * MeSH
• protonové ATPasy * MeSH
• Saccharomyces cerevisiae - proteiny MeSH
• sitosteroly MeSH
• steroly * MeSH
• stigmasterol MeSH

Mitochondrial morphology is an important parameter of cellular fitness. Although many approaches are available for assessing mitochondrial morphology in mammalian cells, only a few technically demanding and laborious methods are available for yeast cells. A robust, fully automated and user-friendly approach that would allow (1) segmentation of tubular and spherical mitochondria in the yeast Saccharomyces cerevisiae from conventional wide-field fluorescence images and (2) quantitative assessment of mitochondrial morphology is lacking. To address this, we compared Global thresholding segmentation with deep learning MitoSegNet segmentation, which we retrained on yeast cells. The deep learning model outperformed the Global thresholding segmentation. We applied it to segment mitochondria in strain lacking the MMI1/TMA19 gene encoding an ortholog of the human TCTP protein. Next, we performed a quantitative evaluation of segmented mitochondria by analyses available in ImageJ/Fiji and by MitoA analysis available in the MitoSegNet toolbox. By monitoring a wide range of morphological parameters, we described a novel mitochondrial phenotype of the mmi1Δ strain after its exposure to oxidative stress compared to that of the wild-type strain. The retrained deep learning model, all macros applied to run the analyses, as well as the detailed procedure are now available at https://github.com/LMCF-IMG/Morphology_Yeast_Mitochondria .

• Klíčová slova
• Deep learning, Mitochondria, Mmi1, Oxidative stress, TCTP, Yeast,
• MeSH
• deep learning MeSH
• fluorescenční mikroskopie metody   MeSH
• mitochondrie * metabolismus   MeSH
• oxidační stres MeSH
• počítačové zpracování obrazu * metody   MeSH
• Saccharomyces cerevisiae - proteiny metabolismus   genetika   MeSH
• Saccharomyces cerevisiae * genetika   metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• Saccharomyces cerevisiae - proteiny MeSH

Homeostasis of cellular membranes is maintained by fine-tuning their lipid composition. Yeast lipid transporter Osh6, belonging to the oxysterol-binding protein-related proteins family, was found to participate in the transport of phosphatidylserine (PS). PS synthesized in the endoplasmic reticulum is delivered to the plasma membrane, where it is exchanged for phosphatidylinositol 4-phosphate (PI4P). PI4P provides the driving force for the directed PS transport against its concentration gradient. In this study, we employed an in vitro approach to reconstitute the transport process into the minimalistic system of large unilamellar vesicles to reveal its fundamental biophysical determinants. Our study draws a comprehensive portrait of the interplay between the structure and dynamics of Osh6, the carried cargo lipid, and the physical properties of the involved membranes, with particular attention to the presence of charged lipids and to membrane fluidity. Specifically, we address the role of the cargo lipid, which, by occupying the transporter, imposes changes in its dynamics and, consequently, predisposes the cargo to disembark in the correct target membrane.

• MeSH
• biologický transport MeSH
• buněčná membrána * metabolismus   MeSH
• fluidita membrány MeSH
• fosfatidylinositolfosfáty metabolismus   MeSH
• fosfatidylseriny metabolismus   MeSH
• proteiny vázající oxysterol MeSH
• Saccharomyces cerevisiae - proteiny * metabolismus   genetika   MeSH
• Saccharomyces cerevisiae metabolismus   MeSH
• steroidní receptory metabolismus   MeSH
• unilamelární lipozómy metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• fosfatidylinositolfosfáty MeSH
• fosfatidylseriny MeSH
• phosphatidylinositol 4-phosphate MeSH Prohlížeč
• proteiny vázající oxysterol MeSH
• Saccharomyces cerevisiae - proteiny * MeSH
• steroidní receptory MeSH
• unilamelární lipozómy MeSH

Trk1 is the main K+ importer of Saccharomyces cerevisiae. Its proper functioning enables yeast cells to grow in environments with micromolar amounts of K+. Although the structure of Trk1 has not been experimentally determined, the transporter is predicted to be composed of four MPM (transmembrane segment - pore loop - transmembrane segment) motifs which are connected by intracellular loops. Of those, in particular the first loop (IL1) is unique in its length; it forms more than half of the entire protein. The deletion of the majority of IL1 does not abolish the transport activity of Trk1. However IL1 is thought to be involved in the modulation of the transporter's functioning. In this work, we prepared a series of internally shortened versions of Trk1 that lacked various parts of IL1, and we studied their properties in S. cerevisiae cells without chromosomal copies of TRK genes. Using this approach, we were able to determine that both N- and C-border regions of IL1 are necessary for the proper localization of Trk1. Moreover, the N-border part of IL1 is also important for the functioning of Trk1, as its absence resulted in a decrease in the transporter's substrate affinity. In addition, in the internal part of IL1, we newly identified a stretch of amino-acid residues that are indispensable for retaining the transporter's maximum velocity, and another region whose deletion affected the ability of Trk1 to adjust its affinity in response to external levels of K+.

• Klíčová slova
• Alkali-metal-cation homeostasis, First intracellular loop, K(+) importer, Regulation, Saccharomyces cerevisiae, Trk1,
• MeSH
• biologický transport MeSH
• draslík * metabolismus   MeSH
• proteiny přenášející kationty * metabolismus   genetika   chemie   MeSH
• Saccharomyces cerevisiae - proteiny * metabolismus   genetika   chemie   MeSH
• Saccharomyces cerevisiae * metabolismus   genetika   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• draslík * MeSH
• proteiny přenášející kationty * MeSH
• Saccharomyces cerevisiae - proteiny * MeSH
• TRK1 protein, S cerevisiae MeSH Prohlížeč

The effectivity of utilization of exogenous sterols in the yeast Saccharomyces cerevisiae exposed to hypoxic stress is dependent on the sterol structure. The highly imported sterols include animal cholesterol or plant sitosterol, while ergosterol, typical of yeasts, is imported to a lesser extent. An elevated utilization of non-yeast sterols is associated with their high esterification and relocalization to lipid droplets (LDs). Here we present data showing that LDs and sterol esterification play a critical role in the regulation of the accumulation of non-yeast sterols in membranes. Failure to form LDs during anaerobic growth in media supplemented with cholesterol or sitosterol resulted in an extremely long lag phase, in contrast to normal growth in media with ergosterol or plant stigmasterol. Moreover, in hem1∆, which mimics anaerobiosis, neither cholesterol nor sitosterol supported the growth in an LD-less background. The incorporation of non-ergosterol sterols into the membranes affected fundamental membrane characteristics such as relative membrane potential, permeability, tolerance to osmotic stress and the formation of membrane domains. Our findings reveal that LDs assume an important role in scenarios wherein cells are dependent on the utilization of exogenous lipids, particularly under anoxia. Given the diverse lipid structures present in yeast niches, LDs fulfil a protective role, mitigating the risk of excessive accumulation of potentially toxic steroids and fatty acids in the membranes. Finally, we present a novel function for sterols in a model eukaryotic cell - alleviation of the lipotoxicity of unsaturated fatty acids.

• Klíčová slova
• Fatty acid, Lipid droplet, Lipotoxicity, Plasma membrane, Relative membrane potential, Sterol,
• MeSH
• anaerobióza MeSH
• buněčná membrána metabolismus   účinky léků   MeSH
• cholesterol metabolismus   MeSH
• ergosterol metabolismus   MeSH
• esterifikace MeSH
• fyziologický stres MeSH
• lipidová tělíska * metabolismus   MeSH
• Saccharomyces cerevisiae - proteiny metabolismus   genetika   MeSH
• Saccharomyces cerevisiae * metabolismus   růst a vývoj   účinky léků   MeSH
• steroly * metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• cholesterol MeSH
• ergosterol MeSH
• Saccharomyces cerevisiae - proteiny MeSH
• steroly * MeSH

Microtubules (MTs) are dynamically unstable polar biopolymers switching between periods of polymerization and depolymerization, with the switch from the polymerization to the depolymerization phase termed catastrophe and the reverse transition termed rescue.1 In presence of MT-crosslinking proteins, MTs form parallel or anti-parallel overlaps and self-assemble reversibly into complex networks, such as the mitotic spindle. Differential regulation of MT dynamics in parallel and anti-parallel overlaps is critical for the self-assembly of these networks.2,3 Diffusible MT crosslinkers of the Ase1/MAP65/PRC1 family associate with different affinities to parallel and antiparallel MT overlaps, providing a basis for this differential regulation.4,5,6,7,8,9,10,11 Ase1/MAP65/PRC1 family proteins directly affect MT dynamics12 and recruit other proteins that locally alter MT dynamics, such as CLASP or kinesin-4.7,13,14,15,16 However, how Ase1 differentially regulates MT stability in parallel and antiparallel bundles is unknown. Here, we show that Ase1 selectively promotes antiparallel MT overlap longevity by slowing down the depolymerization velocity and by increasing the rescue frequency, specifically in antiparallelly crosslinked MTs. At the retracting ends of depolymerizing MTs, concomitant with slower depolymerization, we observe retention and accumulation of Ase1 between crosslinked MTs and on isolated MTs. We hypothesize that the ability of Ase1 to reduce the dissociation of tubulin subunits is sufficient to promote its enrichment at MT ends. A mathematical model built on this idea shows good agreement with the experiments. We propose that differential regulation of MT dynamics by Ase1 contributes to mitotic spindle assembly by specifically stabilizing antiparallel overlaps, compared to parallel overlaps or isolated MTs.

• Klíčová slova
• Ase1/PRC1/MAP65 crosslinkers, diffusible microtubule crosslinkers, microtubule arrays, microtubule dynamics, microtubule overlap stability, microtubules,
• MeSH
• aparát dělícího vřeténka metabolismus   MeSH
• mikrotubuly * metabolismus   MeSH
• proteiny asociované s mikrotubuly * metabolismus   genetika   MeSH
• Saccharomyces cerevisiae - proteiny metabolismus   genetika   MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• Ase1 protein, S cerevisiae MeSH Prohlížeč
• proteiny asociované s mikrotubuly * MeSH
• Saccharomyces cerevisiae - proteiny MeSH

Recycling of 40S ribosomal subunits following translation termination, entailing release of deacylated tRNA and dissociation of the empty 40S from mRNA, involves yeast Tma20/Tma22 heterodimer and Tma64, counterparts of mammalian MCTS1/DENR and eIF2D. MCTS1/DENR enhance reinitiation (REI) at short upstream open reading frames (uORFs) harboring penultimate codons that confer heightened dependence on these factors in bulk 40S recycling. Tma factors, by contrast, inhibited REI at particular uORFs in extracts; however, their roles at regulatory uORFs in vivo were unknown. We examined effects of eliminating Tma proteins on REI at regulatory uORFs mediating translational control of GCN4 optimized for either promoting (uORF1) or preventing (uORF4) REI. We found that the Tma proteins generally impede REI at native uORF4 and its variants equipped with various penultimate codons regardless of their Tma-dependence in bulk recycling. The Tma factors have no effect on REI at native uORF1 and equipping it with Tma-hyperdependent penultimate codons generally did not confer Tma-dependent REI; nor did converting the uORFs to AUG-stop elements. Thus, effects of the Tma proteins vary depending on the REI potential of the uORF and penultimate codon, but unlike in mammals, are not principally dictated by the Tma-dependence of the codon in bulk 40S recycling.

• MeSH
• iniciace translace peptidového řetězce MeSH
• malé podjednotky ribozomu eukaryotické * metabolismus   genetika   MeSH
• messenger RNA * metabolismus   genetika   MeSH
• otevřené čtecí rámce * MeSH
• proteosyntéza MeSH
• Saccharomyces cerevisiae - proteiny * metabolismus   genetika   MeSH
• Saccharomyces cerevisiae * genetika   metabolismus   MeSH
• transkripční faktory bZIP * metabolismus   genetika   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• GCN4 protein, S cerevisiae MeSH Prohlížeč
• messenger RNA * MeSH
• Saccharomyces cerevisiae - proteiny * MeSH
• transkripční faktory bZIP * MeSH

Monovalent-cation homeostasis, crucial for all living cells, is ensured by the activity of various types of ion transport systems located either in the plasma membrane or in the membranes of organelles. A key prerequisite for the functioning of ion-transporting proteins is their proper trafficking to the target membrane. The cornichon family of COPII cargo receptors is highly conserved in eukaryotic cells. By simultaneously binding their cargoes and a COPII-coat subunit, cornichons promote the incorporation of cargo proteins into the COPII vesicles and, consequently, the efficient trafficking of cargoes via the secretory pathway. In this review, we summarize current knowledge about cornichon proteins (CNIH/Erv14), with an emphasis on yeast and mammalian cornichons and their role in monovalent-cation homeostasis. Saccharomyces cerevisiae cornichon Erv14 serves as a cargo receptor of a large portion of plasma-membrane proteins, including several monovalent-cation transporters. By promoting the proper targeting of at least three housekeeping ion transport systems, Na+, K+/H+ antiporter Nha1, K+ importer Trk1 and K+ channel Tok1, Erv14 appears to play a complex role in the maintenance of alkali-metal-cation homeostasis. Despite their connection to serious human diseases, the repertoire of identified cargoes of mammalian cornichons is much more limited. The majority of current information is about the structure and functioning of CNIH2 and CNIH3 as auxiliary subunits of AMPAR multi-protein complexes. Based on their unique properties and easy genetic manipulation, we propose yeast cells to be a useful tool for uncovering a broader spectrum of human cornichons´ cargoes.

• MeSH
• COP-vezikuly metabolismus   MeSH
• homeostáza fyziologie   MeSH
• iontový transport fyziologie   MeSH
• lidé MeSH
• membránové proteiny metabolismus   MeSH
• proteiny přenášející kationty metabolismus   MeSH
• Saccharomyces cerevisiae - proteiny metabolismus   genetika   MeSH
• Saccharomyces cerevisiae * metabolismus   MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• přehledy MeSH
• Názvy látek
• Erv14 protein, S cerevisiae MeSH Prohlížeč
• membránové proteiny MeSH
• proteiny přenášející kationty MeSH
• Saccharomyces cerevisiae - proteiny MeSH

Homologous recombination involves the formation of branched DNA molecules that may interfere with chromosome segregation. To resolve these persistent joint molecules, cells rely on the activation of structure-selective endonucleases (SSEs) during the late stages of the cell cycle. However, the premature activation of SSEs compromises genome integrity, due to untimely processing of replication and/or recombination intermediates. Here, we used a biochemical approach to show that the budding yeast SSEs Mus81 and Yen1 possess the ability to cleave the central recombination intermediate known as the displacement loop or D-loop. Moreover, we demonstrate that, consistently with previous genetic data, the simultaneous action of Mus81 and Yen1, followed by ligation, is sufficient to recreate the formation of a half-crossover precursor in vitro. Our results provide not only mechanistic explanation for the formation of a half-crossover, but also highlight the critical importance for precise regulation of these SSEs to prevent chromosomal rearrangements.

• MeSH
• crossing over (genetika) * MeSH
• DNA vazebné proteiny * metabolismus   genetika   MeSH
• endonukleasy * metabolismus   genetika   MeSH
• homologní rekombinace MeSH
• resolvasy Hollidayova spoje metabolismus   genetika   MeSH
• Saccharomyces cerevisiae - proteiny * metabolismus   genetika   MeSH
• Saccharomyces cerevisiae genetika   metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• DNA vazebné proteiny * MeSH
• endonukleasy * MeSH
• MUS81 protein, S cerevisiae MeSH Prohlížeč
• resolvasy Hollidayova spoje MeSH
• Saccharomyces cerevisiae - proteiny * MeSH
• Yen1 protein, S cerevisiae MeSH Prohlížeč