The bacterial RNA polymerase (RNAP) holoenzyme consists of a catalytic core enzyme (α2ββ′ω) complexed with a σ factor that is required for promoter-specific transcription initiation. During early elongation, the stability of interactions between σ70 (the primary sigma factor in Escherichia coli) and core decreases due to an ordered displacement of segments of σ70 from core triggered by growth of the nascent RNA. Here we demonstrate that the nascent RNA-mediated destabilization of an interaction between σ70 region 4 and the flap domain of the β subunit is required for the bacteriophage λ Q antiterminator protein to contact holoenzyme during early elongation. We demonstrate further that the requirement for nascent RNA in the process by which Q engages RNAP can be bypassed if σ70 region 4 is removed. Our findings illustrate how a regulator can exploit the nascent RNA-mediated reconfiguration of the holoenzyme to gain access to the enzyme during early elongation.
All Science Journal Classification (ASJC) codes
- Molecular Biology
- Cell Biology