Fluctuations in the numbers of proteins are inherent to any biological system. The main cause of these fluctuations is gene expression noise. Controlling gene expression noise could increase robustness and output of a given pathway. In eukaryotes the main sources of noise are long-lived on- and off-states of promoters. By tuning promoter activity and transcript stability of a given gene I developed a system to regulate the gene expression noise at a given mean expression level. I apply this system to genes of the Saccharomyces cerevisiae mating pathway to analyze the effects of perturbations of the number of pathway components.