Comprehensive analysis reveals how single nucleotides contribute to noncoding RNA function in bacterial quorum...

Area of Science:

• Microbiology
• Molecular Biology
• Genetics

Background:

• Quorum sensing in Vibrio harveyi relies on Qrr1-5 small RNAs (sRNAs) to regulate gene expression.
• These sRNAs control approximately 20 mRNA targets through four distinct regulatory mechanisms.
• The precise role of individual nucleotides in sRNA-mediated gene regulation remains largely uncharacterized.

Purpose of the Study:

• To identify nucleotides essential for the function of Qrr4, a small RNA in Vibrio harveyi.
• To elucidate the specific roles of these nucleotides in mRNA target selection and regulatory mechanism.
• To map nucleotide importance for Qrr4's interaction with its mRNA targets, luxR and luxO.

Main Methods:

• Development and application of RSort-Seq, a method combining saturating mutagenesis, fluorescence-activated cell sorting, high-throughput sequencing, and mutual information theory.
• Utilizing companion biochemical assays to determine the molecular mechanisms underlying nucleotide function.
• Analyzing the regulatory impact of every nucleotide within Qrr4 on the expression of luxR and luxO mRNA.

Main Results:

• RSort-Seq generated a detailed map of nucleotides in Qrr4 crucial for stability, Hfq interaction, stem-loop formation, and base pairing with luxR and luxO.
• Specific nucleotides were identified as vital for binding to luxR only, luxO only, or both targets.
• The identified critical nucleotides and their functions differed significantly from predictions made by standard RNA-folding algorithms.

Conclusions:

• RSort-Seq is a powerful approach for dissecting nucleotide-level functions in small RNA regulation.
• This study provides a comprehensive understanding of Qrr4's regulatory elements, challenging existing models.
• The methodology is broadly applicable to studying RNA-RNA interactions in diverse biological systems, including bacteria and higher organisms.