Screen for mutations that affect noise. (A) Promoters used to generate the library. Shown is the noise of each nonmutated promoter as a function of its mean expression. The ratio of nucleosome occupancy close to the TSS and further upstream (Methods) is depicted in color code. Promoters with a low occupancy ratio are DPN type, whereas promoters with a high ratio are OPN. (Squares) Promoters with a conserved TATA box based on Basehoar et al. (2004). (B) Screen design: 400 bp upstream of the ATG of each yeast promoter were cloned, mutated using random PCR, and placed upstream of a yellow fluorescent protein. Expression and noise from single colonies were measured using flow cytometry. (C) Mean expression and noise for all variants in ERG6 promoter library. (Error bars) Standard error of three biological repeats.
