Abstract
ABSTRACTHere, we screened a 10,371 library of diverse molecules using a drug-sensitive fission yeast strain to identify compounds which cause defects in chromosome segregation during mitosis. We identified a phosphorium-ylide-based compound Cutin-1 which inhibits nuclear envelope expansion and nuclear elongation during the closed mitosis of fission yeast, and showed that its target is the β-subunit of fatty acid synthase. A point mutation in the dehydratase domain of Fas1 conferred in vivo and in vitro resistance to Cutin-1. Time-lapse photomicrography showed that the bulk of the chromosomes were only transiently separated during mitosis, and nucleoli separation was defective. Subsequently sister chromatids re-associated leading to chromosomal mis-segregation. These segregation defects were reduced when the nuclear volume was increased and were increased when the nuclear volume was reduced. We propose that there needs to be sufficient nuclear volume to allow the nuclear elongation necessary during a closed mitosis to take place for proper chromosome segregation, and that inhibition of fatty acid synthase compromises nuclear elongation and leads to defects in chromosomal segregation.
Highlights
Genes required for the onset and progression through mitosis have been identified by screens for conditional mutants that are unable to complete cell division
We used this strain to screen for chemical compounds that result in chromosome missegregation and have identified a new inhibitor Cutin-1. This compound restricts nuclear expansion during the closed mitosis of fission yeast, and by using genetic approaches we have shown that the target of Cutin-1 is Fas1, a subunit of fatty acid synthase (FAS)
FAS activity is essential for nuclear envelope expansion (Yam et al, 2011)
Summary
Genes required for the onset and progression through mitosis have been identified by screens for conditional mutants that are unable to complete cell division. The first screens were for temperature-sensitive cdc (cell division cycle) mutants in the budding yeast (Culotti and Hartwell, 1971; Hartwell, 1971), which identified genes required for mitosis. A network of genes regulating the activity of. Genes required for progression through mitosis have been primarily identified in fission yeast through genetic screens for cut (cell untimely torn) mutants, resulting in an un-coordinated mitosis in which the nucleus does not divide but the cell is divided by the septum cutting across the nucleus (Hirano et al, 1986). The characterization and analysis of cut mutants has revealed molecules that are important for chromosome condensation, sister-chromatid separation, anaphase-promoting proteolysis and fatty acid metabolism, as well as other processes (Yanagida, 1998)
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