Figure 2. Relationship between transcriptional noise and promoter architecture in yeast genes.

(A) Plot of the variance compared with mean mRNA copy number for various yeast genes studied by single-molecule FISH reveals two modes of expression: ‘bursty’ (high variance, blue) and constitutive (Poisson-limited variance, red). Housekeeping genes all fall in the constitutive class. All but one cell-cycle-regulated and signal response genes fall in the ‘bursty’ class. Data adapted from Lionnet et al [35]. (B) Promoters of ‘bursty’ genes have a covered architecture (blue), whereas constitutively expressed genes display a pronounced nucleosome-depleted region (red). Data from Lee et al [91], solid line for each class is the average of the genes from panel A, shaded area indicates mean ± s.e.m. TSS, transcription start site.