RT Journal Article SR Electronic T1 Random Sequences Rapidly Evolve into De Novo Promoters JF bioRxiv FD Cold Spring Harbor Laboratory SP 111880 DO 10.1101/111880 A1 Avihu H. Yona A1 Eric J. Alm A1 Jeff Gore YR 2017 UL http://biorxiv.org/content/early/2017/05/09/111880.abstract AB How do new promoters evolve? The current notion is that new promoters emerge from duplication of existing promoters. To test whether promoters can instead evolve de novo, we replaced the lac promoter of Escherichia coli with various random sequences and evolved the cells in the presence of lactose. We found that a typical random sequence of ∼100 bases can mimic the canonical promoter and enable growth on lactose by acquiring only one mutation. We further found that ∼10% of random sequences could serve as active promoters even without any period of evolutionary adaptation. Such a short distance from a random sequence to an active promoter may improve evolvability yet it may also lead to undesirable accidental expression. Nevertheless, across the E. coli genome accidental expression is largely avoided by disfavoring codon combinations that resemble canonical promoter motifs. Our results suggest that the promoter recognition machinery have been tuned to allow high accessibility to new promoters, and similar findings might also be observed in higher organisms or in other motif recognition machineries, like transcription factor binding sites or protein-protein interactions.