Single Molecule Studies of a Novel Mechanism of Bacterial Transcription Initiation

In bacteria, gene transcription begins with the binding of an RNA polymerase (RNAP) core enzyme to the initiation factor σ, which allows it to recognize promoter sequences on the DNA and initiate RNA synthesis. In the canonical transcription cycle, upon reaching the termination sequence and releasing the transcript, RNAP detaches from the DNA and is free to restart the process. However, previous work in our lab has shown that following termination, bacterial RNAP frequently remains bound to the DNA template, and sometimes exhibits one-dimensional sliding over thousands of basepairs. Moreover, in the presence of free σ factor molecules in solution, the sliding, DNA-bound polymerase is often observed to restart transcription. This mechanism of transcription initiation might have implications for the transcriptional coupling of nearby genes.
In this talk, I will describe single-molecule fluorescence-microscopy experiments we are doing to further characterize this novel mechanism of transcription initiation in vitro, and to evaluate its role in the coupling and coordination of gene expression.