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 in the same regulatory pathway, 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. 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 to regulate lipid metabolism and mitotic fidelity in fission yeast.

• MeSH
• Lipid Metabolism * genetics   MeSH
• Mitosis * genetics   MeSH
• Gene Expression Regulation, Fungal * MeSH
• Schizosaccharomyces pombe Proteins * genetics   metabolism   MeSH
• Schizosaccharomyces * genetics   metabolism   MeSH
• Transcription Factors genetics   metabolism   MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Schizosaccharomyces pombe Proteins * MeSH
• Transcription Factors MeSH

Fission yeast 'cut' mutants show defects in temporal coordination of nuclear division with cytokinesis, resulting in aberrant mitosis and lethality. Among other causes, the 'cut' phenotype can be triggered by genetic or chemical perturbation of lipid metabolism, supposedly resulting in shortage of membrane phospholipids and insufficient nuclear envelope expansion during anaphase. Interestingly, penetrance of the 'cut' phenotype in mutants of the transcription factor cbf11 and acetyl-coenzyme A carboxylase cut6, both related to lipid metabolism, is highly dependent on growth media, although the specific nutrient(s) affecting 'cut' occurrence is not known. In this study, we set out to identify the growth media component(s) responsible for 'cut' phenotype suppression in Δcbf11 and cut6-621 cells. We show that mitotic defects occur rapidly in Δcbf11 cells upon shift from the minimal EMM medium ('cut' suppressing) to the complex YES medium ('cut' promoting). By growing cells in YES medium supplemented with individual EMM components, we identified ammonium chloride, an efficiently utilized nitrogen source, as a specific and potent suppressor of the 'cut' phenotype in both Δcbf11 and cut6-621. Furthermore, we found that ammonium chloride boosts lipid droplet formation in wild-type cells. Our findings suggest a possible involvement of nutrient-responsive signaling in 'cut' suppression.

• MeSH
• Acetyl-CoA Carboxylase genetics   MeSH
• Ammonium Chloride chemistry   metabolism   pharmacology   MeSH
• Phenotype MeSH
• Culture Media chemistry   MeSH
• Lipid Droplets drug effects   metabolism   MeSH
• Lipid Metabolism drug effects   genetics   MeSH
• Mitosis drug effects   genetics   MeSH
• Mutation MeSH
• Penetrance MeSH
• Schizosaccharomyces pombe Proteins genetics   MeSH
• Schizosaccharomyces drug effects   genetics   growth & development   metabolism   MeSH
• Transcription Factors genetics   MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Acetyl-CoA Carboxylase MeSH
• Cbf11 protein, S pombe MeSH Browser
• Ammonium Chloride MeSH
• Culture Media MeSH
• Schizosaccharomyces pombe Proteins MeSH
• Transcription Factors MeSH

For every eukaryotic cell to grow and divide, intricately coordinated action of numerous proteins is required to ensure proper cell-cycle progression. The fission yeast Schizosaccharomyces pombe has been instrumental in elucidating the fundamental principles of cell-cycle control. Mutations in S. pombe 'cut' (cell untimely torn) genes cause failed coordination between cell and nuclear division, resulting in catastrophic mitosis. Deletion of cbf11, a fission yeast CSL transcription factor gene, triggers a 'cut' phenotype, but the precise role of Cbf11 in promoting mitotic fidelity is not known. We report that Cbf11 directly activates the transcription of the acetyl-coenzyme A carboxylase gene cut6, and the biotin uptake/biosynthesis genes vht1 and bio2, with the former 2 implicated in mitotic fidelity. Cbf11 binds to a canonical, metazoan-like CSL response element (GTGGGAA) in the cut6 promoter. Expression of Cbf11 target genes shows apparent oscillations during the cell cycle using temperature-sensitive cdc25-22 and cdc10-M17 block-release experiments, but not with other synchronization methods. The penetrance of catastrophic mitosis in cbf11 and cut6 mutants is nutrient-dependent. We also show that drastic decrease in biotin availability arrests cell proliferation but does not cause mitotic defects. Taken together, our results raise the possibility that CSL proteins play conserved roles in regulating cell-cycle progression, and they could guide experiments into mitotic CSL functions in mammals.

• Keywords
• Schizosaccharomyces pombe, biotin, catastrophic mitosis, cut, periodic gene expression, premature cytokinesis, transcription factor,
• MeSH
• Biotin metabolism   MeSH
• DNA, Fungal metabolism   MeSH
• Epistasis, Genetic MeSH
• Transcription, Genetic MeSH
• Genes, Fungal * MeSH
• Mitosis genetics   MeSH
• Mutation genetics   MeSH
• Promoter Regions, Genetic MeSH
• Gene Expression Regulation, Fungal * MeSH
• Schizosaccharomyces pombe Proteins genetics   metabolism   MeSH
• Schizosaccharomyces cytology   genetics   MeSH
• Protein Binding genetics   MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Biotin MeSH
• DNA, Fungal MeSH
• Schizosaccharomyces pombe Proteins MeSH

BACKGROUND: Cbf11 and Cbf12, the fission yeast CSL transcription factors, have been implicated in the regulation of cell-cycle progression, but no specific roles have been described and their target genes have been only partially mapped. METHODOLOGY/PRINCIPAL FINDINGS: Using a combination of transcriptome profiling under various conditions and genome-wide analysis of CSL-DNA interactions, we identify genes regulated directly and indirectly by CSL proteins in fission yeast. We show that the expression of stress-response genes and genes that are expressed periodically during the cell cycle is deregulated upon genetic manipulation of cbf11 and/or cbf12. Accordingly, the coordination of mitosis and cytokinesis is perturbed in cells with genetically manipulated CSL protein levels, together with other specific defects in cell-cycle progression. Cbf11 activity is nutrient-dependent and Δcbf11-associated defects are mitigated by inactivation of the protein kinase A (Pka1) and stress-activated MAP kinase (Sty1p38) pathways. Furthermore, Cbf11 directly regulates a set of lipid metabolism genes and Δcbf11 cells feature a stark decrease in the number of storage lipid droplets. CONCLUSIONS/SIGNIFICANCE: Our results provide a framework for a more detailed understanding of the role of CSL proteins in the regulation of cell-cycle progression in fission yeast.

• MeSH
• Cytokinesis MeSH
• Stress, Physiological MeSH
• Mitogen-Activated Protein Kinases genetics   MeSH
• Mitosis MeSH
• Cyclic AMP-Dependent Protein Kinases genetics   MeSH
• Gene Expression Regulation, Fungal MeSH
• Schizosaccharomyces pombe Proteins genetics   metabolism   MeSH
• Schizosaccharomyces genetics   metabolism   MeSH
• Gene Expression Profiling methods   MeSH
• Transcription Factors genetics   metabolism   MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Cbf11 protein, S pombe MeSH Browser
• Cbf12 protein, S pombe MeSH Browser
• Mitogen-Activated Protein Kinases MeSH
• Cyclic AMP-Dependent Protein Kinases MeSH
• Schizosaccharomyces pombe Proteins MeSH
• sty1 protein, S pombe MeSH Browser
• Transcription Factors MeSH

BACKGROUND: Transcription factors of the CSL (CBF1/RBP-Jk/Suppressor of Hairless/LAG-1) family are key regulators of metazoan development and function as the effector components of the Notch receptor signalling pathway implicated in various cell fate decisions. CSL proteins recognize specifically the GTG[G/A]AA sequence motif and several mutants compromised in their ability to bind DNA have been reported. In our previous studies we have identified a number of novel putative CSL family members in fungi, organisms lacking the Notch pathway. It is not clear whether these represent genuine CSL family members. METHODOLOGY/PRINCIPAL FINDINGS: Using a combination of in vitro and in vivo approaches we characterized the DNA binding properties of Cbf11 and Cbf12, the antagonistic CSL paralogs from the fission yeast, important for the proper coordination of cell cycle events and the regulation of cell adhesion. We have shown that a mutation of a conserved arginine residue abolishes DNA binding in both CSL paralogs, similar to the situation in mouse. We have also demonstrated the ability of Cbf11 and Cbf12 to activate gene expression in an autologous fission yeast reporter system. CONCLUSIONS/SIGNIFICANCE: Our results indicate that the fission yeast CSL proteins are indeed genuine family members capable of functioning as transcription factors, and provide support for the ancient evolutionary origin of this important protein family.

• MeSH
• Active Transport, Cell Nucleus MeSH
• Cell Cycle MeSH
• DNA, Fungal metabolism   MeSH
• Conserved Sequence MeSH
• Mutation MeSH
• Genes, Reporter genetics   MeSH
• Response Elements genetics   MeSH
• Schizosaccharomyces pombe Proteins chemistry   genetics   metabolism   MeSH
• Schizosaccharomyces cytology   genetics   metabolism   MeSH
• Base Sequence MeSH
• Sequence Homology, Amino Acid MeSH
• Transcription Factors chemistry   genetics   metabolism   MeSH
• Animals MeSH
• Check Tag
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• DNA, Fungal MeSH
• Schizosaccharomyces pombe Proteins MeSH
• Transcription Factors MeSH