Mycobacterial HelD is a nucleic acids-clearing factor for RNA polymerase

Area of Science:

• Molecular Biology
• Structural Biology
• Biochemistry

Background:

• RNA polymerase (RNAP) requires accessory factors for regulation and recovery from stalled states.
• Understanding these factors is key to controlling gene expression, particularly in medically relevant bacteria like mycobacteria.

Purpose of the Study:

• To investigate the mechanism of RNA polymerase (RNAP) recycling by the helicase-like factor HelD.
• To elucidate the structural basis of HelD-mediated RNAP regulation.

Main Methods:

• Cryo-electron microscopy (cryo-EM) to determine the structure of the RNAP-HelD complex.
• Biochemical assays to assess HelD's function in preventing non-specific DNA interactions and dissociating stalled complexes.

Main Results:

• A cryo-EM structure reveals HelD binding to RNAP, occupying nucleic acid binding and substrate delivery channels.
• HelD locks RNAP in an inactive state, preventing non-specific DNA binding and dissociating stalled transcription elongation complexes.
• HelD acts as a clearing factor, releasing RNAP for dormancy or re-initiation of transcription.

Conclusions:

• HelD is a crucial factor for RNAP recycling and transcriptional regulation in mycobacteria.
• The structural insights into the HelD-RNAP complex provide a mechanistic understanding of transcription control.
• HelD's role as a clearing factor has implications for understanding mycobacterial gene expression and potential therapeutic strategies.