A transcription antiterminator constructs a NusA-dependent shield to the emerging transcript

Area of Science:

• Bacteriology
• Molecular Biology
• Virology

Background:

• The bacterial transcription elongation factor NusA plays a dual role in RNA polymerase activity.
• NusA can induce transcription pausing and termination independently.
• NusA also acts as a cofactor for antiterminator proteins that counteract these effects.

Purpose of the Study:

• To investigate the role of NusA in the function of the lambda-related phage 82 antiterminator Q(82).
• To elucidate the mechanism by which Q(82) prevents transcription termination.
• To differentiate the distinct activities of antiterminators.

Main Methods:

• In vitro transcription assays.
• Analysis of stable complex formation between Q(82), NusA, and RNA polymerase.
• Investigating the role of NusA in Q(82)'s antipausing activity.

Main Results:

• NusA is required for Q(82) to form a stable complex that restricts access of termination mechanisms to the nascent transcript.
• This complex formation suggests a localization of Q(82) and NusA near the beta flap domain of RNA polymerase.
• NusA is not required for Q(82)'s antipausing activity in vitro.

Conclusions:

• Antiterminators like Q(82) possess at least two distinct activities: antipausing and RNA occlusion.
• RNA occlusion, mediated by NusA, is crucial for Q(82) to prevent termination.
• These findings provide insight into the complex regulatory mechanisms of phage transcription.