Restriction of Lte1 to the bud cortex depends on the cortical proteins Cdc42 and Kel1 and the septin ring. Cla4 and Cdc14 promote and demote Lte1 localization at and from the bud cortex, respectively, suggesting not only that the phosphorylation status of Lte1 controls its localization but also indicating that Cla4 and Cdc14 are key regulators of the spatial asymmetry of Lte1.

In the Saccharomyces cerevisiae pheromone-response pathway, the transcription factor Ste12 is inhibited by two MAP kinase-responsive regulators, Dig1 and Dig2. These two related proteins bind to distinct regions of Ste12 but are redundant in their inhibition of Ste12-dependent gene expression. Here we describe three unexpected functions for Dig1 that are non-redundant with those of Dig2. First, the removal of Dig1 results in a specific increase in intrinsic and extrinsic noise in the transcriptional outputs of the mating pathway. Second, in dig1Δ cells, Ste12 relocalizes from the nucleoplasmic distribution seen in wild-type cells into discrete subnuclear foci. Third, genome-wide iChIP studies revealed that Ste12-dependent genes display increased interchromosomal interactions in dig1Δ cells. These findings suggest that the regulation of gene expression through long-range gene interactions, a widely-observed phenomenon, comes at the cost of increased noise. Consequently, cells may have evolved mechanisms to suppress noise by controlling these interactions.