It is well known that chromatin regulators affect gene expression, but most studies to date have only investigated the requirement of such proteins in steady-state transcription. For example, characterization of large collections of yeast mutants has shown that individual deletion of chromatin regulators affects the transcription of small numbers of genes when yeast are grown in rich media. Now, Oliver Rando and colleagues analyze the effect of 83 histone mutants on 170 transcripts in yeast grown under conditions of diamide stress (PLoS Biol. 10, e1001369, 2012). During a time course following introduction of diamide stress, the authors found that most chromatin regulator mutants affected the expression of many more genes during the stress response than were altered in wild-type yeast. The authors noted that there were two major classes of mutants: those that show 'hyper-responsive' transcription under diamide stress and those that show 'hypo-responsive' transcription under stress. Single-cell analysis of gene expression was performed using microscopy of GFP-tagged proteins, and the authors observed that induction of GFP generally followed a sigmoid curve that resolved into baseline levels of production. These results are best explained by a simple model of a diamide-induced response and gradual decay of mRNA.
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