title: Cellular morphogenesis under stress is influenced by the sphingolipid pathway gene ISC1 and DNA integrity checkpoint genes in Saccharomyces cerevisiae.
abstract: In Saccharomyces cerevisiae, replication stress induced by hydroxyurea (HU) and methyl methanesulfonate (MMS) activates DNA integrity checkpoints; in checkpoint-defective yeast strains, HU treatment also induces morphological aberrations. We find that the sphingolipid pathway gene ISC1, the product of which catalyzes the generation of bioactive ceramides from complex sphingolipids, plays a novel role in determining cellular morphology following HU/MMS treatment. HU-treated isc1Δ cells display morphological aberrations, cell-wall defects, and defects in actin depolymerization. Swe1, a morphogenesis checkpoint regulator, and the cell cycle regulator Cdk1 play key roles in these morphological defects of isc1Δ cells. A genetic approach reveals that ISC1 interacts with other checkpoint proteins to control cell morphology. That is, yeast carrying deletions of both ISC1 and a replication checkpoint mediator gene including MRC1, TOF1, or CSM3 display basal morphological defects, which increase following HU treatment. Interestingly, strains with deletions of both ISC1 and the DNA damage checkpoint mediator gene RAD9 display reduced morphological aberrations irrespective of HU treatment, suggesting a role for RAD9 in determining the morphology of isc1Δ cells. Mechanistically, the checkpoint regulator Rad53 partially influences isc1Δ cell morphology in a dosage-dependent manner.
authors.affiliation: Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, South Carolina 29425, USA.
authors.forename: Kaushlendra
authors.initials: K
authors.lastname: Tripathi
authors.forename: Nabil
authors.initials: N
authors.lastname: Matmati
authors.forename: W Jim
authors.initials: WJ
authors.lastname: Zheng
authors.forename: Yusuf A
authors.initials: YA
authors.lastname: Hannun
authors.forename: Bidyut K
authors.initials: BK
authors.lastname: Mohanty
mesh_terms: D000199:Actins / Q000378:metabolism; D015153:Blotting, Western; D017489:CDC28 Protein Kinase, S cerevisiae / Q000235:genetics / Q000378:metabolism; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism; D002473:Cell Wall / Q000187:drug effects / Q000378:metabolism; D002686:Chitin / Q000378:metabolism; D004249:DNA Damage; D004260:DNA Repair; D004261:DNA Replication / Q000187:drug effects; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D006918:Hydroxyurea / Q000633:toxicity; D008741:Methyl Methanesulfonate / Q000633:toxicity; D008856:Microscopy, Fluorescence; D009153:Mutagens / Q000633:toxicity; D009154:Mutation; D019384:Nucleic Acid Synthesis Inhibitors / Q000633:toxicity; D011505:Protein-Tyrosine Kinases / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000187:drug effects / Q000235:genetics* / Q000254:growth & development; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics* / Q000378:metabolism; D013107:Sphingolipids / Q000378:metabolism; D010738:Type C Phospholipases / Q000235:genetics* / Q000378:metabolism
chemical_list: D000199:Actins; D018797:Cell Cycle Proteins; C508610:Csm3p protein, S cerevisiae; D004268:DNA-Binding Proteins; C441579:MRC1 protein, S cerevisiae; D009153:Mutagens; D019384:Nucleic Acid Synthesis Inhibitors; D029701:Saccharomyces cerevisiae Proteins; D013107:Sphingolipids; C119636:TOF1 protein, S cerevisiae; C069930:rad9 protein; D002686:Chitin; D008741:Methyl Methanesulfonate; C099685:SWE1 protein, S cerevisiae; D011505:Protein-Tyrosine Kinases; D017489:CDC28 Protein Kinase, S cerevisiae; C419391:ISC1 protein, S cerevisiae; D010738:Type C Phospholipases; D006918:Hydroxyurea