An Iterative, Synthetic Approach To Engineer a High-Performance PhoB-Specific Reporter
Abstract
Transcriptional reporters are common tools for analyzing either the transcription of a gene of interest or the activity of a specific transcriptional regulator. Unfortunately, the latter application has the shortcoming that native promoters did not evolve as optimal readouts for the activity of a particular regulator. We sought to synthesize an optimized transcriptional reporter for assessing PhoB activity, aiming for maximal "on" expression when PhoB is active, minimal background in the "off" state, and no control elements for other regulators. We designed specific sequences for promoter elements with appropriately spaced PhoB-binding sites, and at 19 additional intervening nucleotide positions for which we did not predict sequence-specific effects, the bases were randomized. Eighty-three such constructs were screened in Vibrio fischeri, enabling us to identify bases at particular randomized positions that significantly correlated with high-level "on" or low-level "off" expression. A second round of promoter design rationally constrained 13 additional positions, leading to a reporter with high-level PhoB-dependent expression, essentially no background, and no other known regulatory elements. As expressed reporters, we used bot...Continue Reading
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A lasting symbiosis: how Vibrio fischeri finds a squid partner and persists within its natural host.
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