Fig. 6:

Purine-rich coding sequences protect runaway RNAP from Rho. a, Beta-galactosidase (LacZ) assays for termination of native and recoded human growth hormone (HGH) coding sequence in wild-type and Δrho B. subtilis, as in Fig. 2c. Colored bars summarize result: grey, no termination; purple, Rho termination; pink, Rho-independent termination. Insert sequences will be available in Supplementary Table 2. Uncropped plate image is available in Extended Data Fig. 4b. b, Average excess purine content in leading strand gene sequences across n = 1,364 bacterial genomes that encode Rho, separated by phylum-level prediction of runaway or coupled transcription³² (Methods). Purine excess quantifies the difference between purine and pyrimidine counts, normalized to length (Methods). Median, 25^th, 75^th percentiles marked by horizontal lines. c, Schematic of sequence-based selection of Rho targets during runaway transcription. Purine-rich genes are protected by Rho’s pyrimidine preference, while base pairing dictates that the antisense strand is enriched for pyrimidines, promoting Rho termination.