Structural insights into NusG regulating transcription elongation

Area of Science:

• Molecular Biology
• Structural Biology
• Microbiology

Background:

• NusG is a crucial transcription factor regulating bacterial transcription.
• It enhances RNA polymerase (RNAP) processivity and couples transcription with translation.

Purpose of the Study:

• To determine the structure of the Escherichia coli RNA polymerase-NusG complex.
• To elucidate the molecular mechanism by which NusG enhances transcription.

Main Methods:

• X-ray crystallography to obtain the high-resolution structure of the RNAP-NusG complex.
• Structural analysis and modeling to understand NusG's interaction with RNAP.

Main Results:

• The structure reveals NusG's N-terminal domain (NGN) binds to the RNAP central cleft.
• NGN interacts with specific RNAP subunits (β' clamp helices, β protrusion, β lobe), distinct from archaeal complexes.
• A model of the complete NusG-transcription elongation complex suggests NGN stabilizes the upstream fork junction.

Conclusions:

• NusG's interaction with RNAP stabilizes the transcription elongation complex.
• This stabilization mechanism, involving NGN binding to the fork junction, enhances RNAP processivity and transcription efficiency.