Biology subjects

Princova, J.

Publications and source records attributed to Princova, J..

3 recordsLinked to original sources

bioRxiv2022

Altered cohesin dynamics and histone H3K9 modifications contribute to mitotic defects in the cbf11Δ lipid metabolism mutant

Mitotic fidelity is crucial for the faithful distribution of genetic information into the daughter cells. Many fungal species, including the fission yeast Schizosaccharomyces pombe, undergo a closed form of mitosis, during which the nuclear envelope does not break down. In S. pombe numerous processes have been identified that contribute to successful completion of mitosis. Notably, perturbations of lipid metabolism can lead to catastrophic mitosis and the "cut" phenotype. It was suggested that these mitotic defects are caused by insufficient membrane phospholipid supply during the anaphase nuclear expansion. However, it is not clear whether additional factors are involved. In this study we characterized in detail the mitosis in an S. pombe mutant lacking the Cbf11 transcription factor, which regulates lipid metabolism genes. We show that in cbf11{Delta} cells mitotic defects appear already prior to anaphase, before the nuclear expansion begins. Moreover, we identify altered cohesin dynamics and centromeric chromatin structure as additional factors affecting mitotic fidelity in cells with disrupted lipid homeostasis, providing new insights into this fundamental biological process.

cell 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↗