Alternative transcription cycle for bacterial RNA polymerase.

Area of Science:

• Molecular Biology
• Genetics
• Biochemistry

Background:

• Gene transcription is a fundamental biological process.
• RNA polymerases (RNAPs) are key enzymes in transcription.
• The canonical model describes RNAP dissociation after transcription termination.

Purpose of the Study:

• To investigate the behavior of RNA polymerases after transcript termination.
• To determine if RNAPs rebind DNA or dissociate after termination.
• To explore alternative transcription cycles and their regulatory implications.

Main Methods:

• Single-molecule fluorescence microscopy to observe individual RNAP molecules.
• Genome-wide RNA sequencing in live cells to detect secondary initiation events.

Main Results:

• Following termination, RNAPs predominantly remain DNA-bound.
• RNAPs exhibit one-dimensional sliding along DNA after termination.
• DNA-bound RNAPs frequently reinitiate transcription, often in the reverse direction, producing antisense transcripts.

Conclusions:

• An alternative transcription cycle exists where RNAPs reinitiate without dissociating from DNA.
• This post-termination DNA-bound reinitiation is observed in vivo.
• This mechanism has significant implications for gene regulation and antisense transcript production.