Low Concentrations of Trifluoperazine Arrest the Cell Division Cycle of Saccharomyces cerevisiae at Two Specific Stages

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Abstract
Low concentrations of trifluoperazine (TFP) reversibly inhibited vegetative growth of Saccharomyces cerevisiae. The cell cycle was analysed by flow cytometry using haploid a cells synchronized by .alpha.-factor arrest and several temperature-sensitive cell division cycle mutants (cdc). Cells were pulse-labelled with fluorescein-labelled concanavalin A (ConA-FITC) to determine cell division or stained with propidium iodide to determine the stage of cell cycle arrest by TFP. Cell growth was estimated from the changes in the relative intensity of scattered light, and budding was determined microscopically. When TFP was added before Start on release from .alpha.-factor arrest, after release of cdc28-arrested cells, and at transition from stationary phase to vegetative growth, cell growth, budding and DNA synthesis were inhibited. When TFP was added after execution of spindle pole body duplication, cell growth, bud emergence and DNA synthesis were not inhibited but cell division was inhibited and the cells arrested with buds at G2 +M. Using cdc mutants, the second stage of arrest by TFP was determined to be just before medial-nuclear division.