Promoters can be divided into two classes based on their nucleosome architecture and existence
of a TATA box. These two classes differ in three levels: evolvability of their expression, sensitivity to signals and finally cell-to-cell variability in expression ("noise"). Using random mutagenesis, we show that these
promoters also have striking differences in their ability to withstand (or respond to) mutations in the
promoter region, consistent with the different evolvabilities.We further investigate the noise properties of these two promoters and show that sequence differences can (in some cases) impact noise, suggesting that noise in expression may be an evolvable trait.
