lQ interaction with E. coli RNA polymerase for antitermination: Regions of E. coli RNA polymerase required for lQ-mediated antitermination in binding and function

Phage ?Q protein is a transcriptional antiterminator that is required for late gene expression from the pR? promoter when ? prophage decides to follow the lytic pathway. ?Q modifies Escherichia coli RNA polymerase (RNAP) at the early elongation stage. Once engaged, ?Q maintains itself as a subunit of the elongation complex throughout the elongation. Studies show that ?Q confers RNAP resistance to both intrinsic and ?-mediated terminators and less pausing. However, little is known about the interaction between ?Q and RNAP. In this study, the largest subunits (? and ??) of RNAP were examined to map the ?Q binding site. A stronger binding was observed with ? than ??, and the binding site was narrowed to ?501-832. This region was further defined as small as 82 amino acids (?600-681) that interacted with ?Q. In addition, 12 mutant RNAPs were isolated for a reduced ?Q antitermination within the potential ?Q binding regions, specifically near the main channel. These results propose that ?Q modifies the active center of RNAP for antitermination.