Figure 3. Translocation modulators target RNA-DNA hybrid and transcription bubble in bacterial TEC. Top panel: Nun protein of bacteriophage H022 interferes with translocation⁶⁸ by stabilizing the -10 base pair of the hybrid and tethering RNAP to the hybrid. We proposed that the homologous N protein of bacteriophage λ stabilizes the -9 base pair of the hybrid and prevents the -10 base pair to favor translocation. E. coli NusG and its eukaryotic homolog Spt5 promote translocation by facilitating re-annealing of DNA immediately upstream from the 9-bp hybrid. B. subtilis NusG tethers RNAP to pre-translocated register by binding to the middle part of transcription bubble.⁷⁰ σ⁷⁰ subunit interferes with translocation by binding to the “-10-like” sequence at the upstream end of transcription bubble.⁹⁶ Bottom panel: cis-acting RNA hairpin and Switch 3 domain in β subunit promote translocation by preventing expansion of the hybrid to 10-bp length.⁷⁹