SET Domain Protein Regulates S. pombe Cytokinesis Figure 2. hif2, set3, and snt1 deletion mutants are hyper-sensitive to LatA treatment. (A) Ten-fold serial dilutions of logarithmically growing cells of the indicated genotype were plated onto YES plates containing 0.5 mM LatA or DMSO (solvent control) at 30uC for 3 d. (B) Cells of the indicated genotype were grown to mid-log phase at 30uC and then treated with 0.5 mM LatA for 5 h before being fixed and stained with DAPI (nuclei) and aniline blue (cell wall/septa). Bar, 10 mm. (C) Quantitation of phenotypes of cells treated as in B. Between 200 and 500 cells were counted for each genotypic class. doi:10.1371/journal.pone.0031224.g002 efficiency of the block and release was monitored by examining the level of bi-nucleate cells every 30 minutes after shifting from 36uC to 25uC (Figure S3B,C). The levels of Set3-HA, Snt1-HA, Hif2- HA were not significantly altered as a function of cell cycle position (Figure S3A). Taken together, these results are consistent with a model in which the increased activity of the Set3p-Snt1- Hif2p complex is required for a proper cellular response to LatA induced stress. Microarray expression profiling Histone deacetylase complexes have well defined roles in regulating transcription through chromatin modification [23,24]. This suggested a model in which the Set3p complex might affect the transcription of genes involved in regulating cytokinesis or the cytoskeleton. To further explore this hypothesis, expression profiles were generated for both wild-type and set3D mutants. Total RNA was extracted from wild-type or set3D cultures Figure 3. set3 functions in a pathway parallel to those defined by clp1 and lsk1. Cells of the indicated genotype were grown to mid-log phase at 30uC and then treated with 0.1 mM LatA for 5 h before being fixed and stained with DAPI (nuclei) and aniline blue (cell wall/septa). Two hundred cells were counted for each genotypic class. doi:10.1371/journal.pone.0031224.g003 PLoS ONE | www.plosone.org 5 February 2012 | Volume 7 | Issue 2 | e31224