Biology subjects

Maresova, A.

Publications and source records attributed to Maresova, A..

5 recordsLinked to original sources

bioRxiv2024

Cbf11 and Mga2 function as a single regulatory entity to activate transcription of lipid metabolism genes and promote mitotic fidelity in fission yeast

Within a eukaryotic cell, both lipid homeostasis and faithful cell cycle progression are meticulously orchestrated. The fission yeast Schizosaccharomyces pombe provides a powerful platform to study the intricate regulatory mechanisms governing these fundamental processes. In S. pombe, the Cbf11 and Mga2 proteins are transcriptional activators of non-sterol lipid metabolism genes, with Cbf11 also known as a cell cycle regulator. Despite sharing a common set of target genes, little was known about their functional relationship. This study reveals that Cbf11 and Mga2 function together as a single regulatory entity critical for both lipid metabolism and mitotic fidelity. Deletion of either gene results in a similar array of defects, including slow growth, dysregulated lipid homeostasis, impaired cell cycle progression (cut phenotype), abnormal cell morphology, perturbed transcriptomic and proteomic profiles, and compromised response to the stressors camptothecin and thiabendazole. Remarkably, the double deletion mutant does not exhibit a more severe phenotype compared to the single mutants, suggesting that Cbf11 and Mga2 work together in the same pathway. In addition, ChIP-nexus analysis reveals that both Cbf11 and Mga2 bind to nearly identical positions within the promoter regions of target genes. Interestingly, Mga2 binding appears to be dependent on the presence of Cbf11 and Cbf11 likely acts as a tether to DNA, while Mga2 is needed to activate the target genes. In addition, the study explores the distribution of Cbf11 and Mga2 homologs across fungi. The presence of both Cbf11 and Mga2 homologs in Basidiomycota contrasts with Ascomycota, which mostly lack Cbf11 but retain Mga2. This suggests an evolutionary rewiring of the regulatory circuitry governing lipid metabolism and mitotic fidelity. In conclusion, this study offers compelling support for Cbf11 and Mga2 functioning jointly as a single regulator of lipid metabolism and mitotic fidelity in fission yeast. SUMMARY STATEMENTCbf11 and Mga2, transcriptional activators of non-sterol lipid metabolism genes, function as a single regulatory unit and are both required for proper cell cycle progression in the fission yeast Schizosaccharomyces pombe.

molecular biology↗

bioRxiv2023

Nitrogen availability and TOR signalling are important for preventing catastrophic mitosis in fission yeast

Mitosis is a critical stage in the cell cycle, controlled by a vast network of regulators responding to multiple internal and external factors. The fission yeast Schizosaccharomyces pombe may demonstrate catastrophic mitotic phenotypes due to mutations or drug treatments. One of the factors provoking catastrophic mitosis is a disturbed lipid metabolism, resulting from e.g. mutations in acetyl-CoA/biotin carboxylase (cut6), in fatty acid synthase (fas2/lsd1), or in the transcriptional regulator of lipid metabolism (cbf11) genes, as well as treatment with inhibitors of fatty acid synthesis. It was previously shown that mitotic fidelity in lipid metabolism mutants can be partially rescued by ammonium chloride. In this study we demonstrate that mitotic fidelity can be improved by multiple good nitrogen sources. Moreover, this rescue is not limited to lipid metabolism disturbances but also applies to a number of unrelated mitotic mutants. Interestingly, the rescue is not achieved by restoring the lipid metabolism state, but rather indirectly. We found that the TOR regulatory network plays a major role in mediating such rescue, highlighting a novel role for TOR in mitotic fidelity.

cell biology↗

bioRxiv2023

Critical importance of DNA binding for CSL protein functions in fission yeast

CSL (CBF1/RBP-J{kappa}/Suppressor of Hairless/LAG-1) proteins are conserved transcription factors found in animals and fungi. In fission yeast, they regulate various cellular processes, including cell cycle progression, lipid metabolism, and cell adhesion. CSL proteins bind to DNA through their N-terminal Rel-like domain and central beta-trefoil domain. Here, we investigated the importance of DNA binding for CSL functions in the fission yeast Schizosaccharomyces pombe. We created CSL mutants with disrupted DNA binding and found that the vast majority of CSL functions depend on intact DNA binding. Specifically, DNA binding is crucial for the regulation of cell adhesion, lipid metabolism, cell cycle progression, long non-coding RNA expression, and genome integrity maintenance. Interestingly, perturbed lipid metabolism leads to chromatin structure changes, potentially linking lipid metabolism to the diverse CSL-associated phenotypes. Our study highlights the critical role of DNA binding for CSL protein functions in fission yeast. SUMMARY STATEMENTCSL transcription factors regulate a diverse set of processes, but the mechanisms are not always clear. We show that S. pombe CSL proteins need the ability to bind DNA for most of their roles.

molecular biology↗

bioRxiv2022

SAGA histone acetyltransferase module facilitates chromatin accessibility to SMC5/6

Structural Maintenance of Chromosomes (SMC) complexes are molecular machines driving chromatin organization at higher levels. In eukaryotes, three SMC complexes (cohesin, condensin, and SMC5/6) play key roles in cohesion, condensation, replication, transcription and DNA repair. Here, we performed a genetic screen in fission yeast to identify novel factors required for SMC5/6 binding to DNA. We identified 79 genes of which histone acetyltransferases (HATs) were the most represented. Genetic and phenotypic analyses suggested a particularly strong functional relationship between the SMC5/6 and SAGA complexes. Furthermore, several SMC5/6 subunits physically interacted with SAGA HAT module components Gcn5 and Ada2. As Gcn5-dependent acetylation facilitates the accessibility of chromatin to DNA repair proteins, we first analysed the formation of DNA damage-induced SMC5/6 foci in the {Delta}gcn5 mutant. The SMC5/6 foci formed normally in {Delta}gcn5, suggesting SAGA-independent SMC5/6 localization to DNA-damaged sites. Next, we used Nse4-FLAG chromatin-immunoprecipitation (ChIP-seq) analysis in unchallenged cells to assess SMC5/6 distribution. A significant portion of SMC5/6 accumulated within gene regions in wild-type cells, which was reduced in {Delta}gcn5 and {Delta}ada2 mutants. The drop in SMC5/6 levels was also observed in gcn5-E191Q acetyltransferase-dead mutant. Altogether, our data suggest that the SAGA HAT module may facilitate chromatin accessibility to SMC5/6 at gene regions. Author SummaryGenomes of all eukaryotes must be folded and packed into their relatively small nuclear spaces. Histones first pack free genomic DNA into nucleosomes and their arrays. Other complexes like histone modifiers and remodelers can regulate nucleosome positions and their packing within chromatin fibres. They assist in the relative opening or condensation of chromatin fibres and facilitate their accessibility to DNA-binding proteins. The highly conserved Structural Maintenance of Chromosomes (SMC) complexes (cohesin, condensin, and SMC5/6) compact further chromatin fibres at higher levels. These molecular machines can loop chromatin fibres, which need access to segments of free DNA for their physical binding to DNA. Here, we studied genetic and physical interactions between histone-modifying SAGA complex and SMC5/6. We show that the SAGA histone acetyltransferase module may facilitate chromatin access to SMC5/6.

genetics↗

bioRxiv2022

Perturbed fatty-acid metabolism is linked to localized chromatin hyperacetylation, increased stress-response gene expression and resistance to oxidative stress

Oxidative stress is associated with cardiovascular and neurodegenerative diseases, diabetes, cancer, psychiatric disorders and aging. In order to counteract, eliminate and/or adapt to the sources of stress, cells possess elaborate stress-response mechanisms, which also operate at the level of regulating transcription. Interestingly, it is becoming apparent that the metabolic state of the cell and certain metabolites can directly control the epigenetic information and gene expression. In the fission yeast Schizosaccharomyces pombe, the conserved Sty1 stress-activated protein kinase cascade is the main pathway responding to most types of stresses, and regulates the transcription of hundreds of genes via the Atf1 transcription factor. Here we report that fission yeast cells defective in fatty acid synthesis (cbf11, mga2 and ACC/cut6 mutants) show increased expression of a subset of stress-response genes. This altered gene expression depends on Sty1, and the Gcn5 and Mst1 histone acetyltransferases, is associated with increased acetylation of histone H3 at lysine 9 in the corresponding gene promoters, and results in increased cellular resistance to oxidative stress. Since both fatty-acid synthesis and histone acetylation compete for the same substrate, acetyl-CoA, we propose that changes in lipid metabolism can regulate the chromatin and transcription of specific stress-response genes, which in turn might help cells to maintain redox homeostasis.

molecular biology↗