High-resolution RNA 3'-ends mapping of bacterial Rho-dependent transcripts

Area of Science:

• Molecular Biology
• Bacterial Genetics
• RNA Biology

Background:

• Bacterial transcription termination occurs via Rho-dependent or Rho-independent (intrinsic) pathways.
• Intrinsic terminators feature stem-loop RNA structures and uridine stretches, ensuring precise transcript 3' ends.
• Rho-dependent terminators lack defined characteristics and are presumed to yield diffuse 3' ends, with protection mechanisms unclear.

Purpose of the Study:

• To precisely map the 3' ends of bacterial transcripts terminated by Rho-dependent and Rho-independent mechanisms in vivo.
• To investigate the structural features and protective roles of Rho-dependent terminators against RNA degradation.

Main Methods:

• High-throughput sequencing to map precise steady-state RNA 3' ends for numerous Escherichia coli genes.
• Bioinformatic analysis to identify terminator structures and Rho-utilization (rut) sites.
• Experimental validation of RNA protection by identified structures against specific exonucleases (PNPase, RNase II).

Main Results:

• Rho-dependent termination in E. coli yields precise RNA 3' ends, contrary to previous assumptions.
• These precise termini are located downstream of stable stem-loop structures, not uridine stretches.
• Evidence suggests these stem-loop structures shield Rho-dependent transcripts from 3'-5' exonucleases.

Conclusions:

• Rho-dependent transcription termination is a precise process in E. coli, governed by specific RNA structures.
• Stable stem-loop structures downstream of rut sites serve as protective elements against exonucleolytic degradation.
• This study provides the first comprehensive in vivo map of precise RNA 3' ends for Rho-dependent transcripts.