Structural insights into RNA-mediated transcription regulation in bacteria

Area of Science:

• Molecular Biology
• Structural Biology
• Genetics

Background:

• RNA can self-regulate its synthesis, with U-rich sequences typically pausing transcription and enabling termination.
• Intrinsic terminators rely on RNA polymerase (RNAP) pausing and transcript release.
• The mechanism by which nascent RNA modulates its own synthesis, particularly suppressing termination, is not well understood.

Purpose of the Study:

• To elucidate the structural mechanisms by which the regulatory RNA putL suppresses transcription pausing and termination.
• To understand how nascent RNA can modulate RNAP activity at U-rich pause sites.

Main Methods:

• Cryo-electron microscopy (cryo-EM) reconstructions of RNAP.
• Analysis of RNAP during transcription of putL variants and unrelated sequences at U-rich pause sites.

Main Results:

• Transcribing U-rich sequences promotes widening of the RNAP nucleic-acid-binding channel.
• This widening destabilizes RNAP-DNA and RNAP-RNA interactions, facilitating transcript dissociation.
• RNAP remains bound to DNA even after transcript release, suggesting a unique termination-release mechanism.

Conclusions:

• The study provides a structural basis for RNA-mediated intrinsic transcription termination.
• PutL suppresses pausing and promotes its own synthesis by modulating RNAP channel dynamics.
• RNA can directly control transcription termination through structural changes in RNAP.