Sequence-specific cleavage of dsRNA by Mini-III RNase

Area of Science:

• Molecular Biology
• Enzymology
• Structural Biology

Background:

• Ribonucleases (RNases) are essential enzymes for RNA processing and degradation.
• Most known RNases exhibit limited substrate specificity, targeting single-stranded RNA or specific structural contexts.
• Sequence-specific cleavage of double-stranded RNA (dsRNA) by RNases has not been previously identified.

Purpose of the Study:

• To investigate the substrate specificity of Bacillus subtilis RNase Mini-III (BsMiniIII) on dsRNA.
• To identify sequence motifs recognized by BsMiniIII for dsRNA cleavage.
• To elucidate the structural basis for sequence-specific dsRNA cleavage by BsMiniIII.

Main Methods:

• Limited enzymatic digestion of long dsRNA from bacteriophage Φ6 using BsMiniIII.
• Analysis of cleavage sites to identify consensus target sequences.
• Determination of essential nucleotide residues and structural elements involved in substrate recognition and cleavage.

Main Results:

• BsMiniIII demonstrates sequence-dependent cleavage of long dsRNA.
• A consensus target sequence was identified, with specific nucleotide residues influencing cleavage efficiency.
• The loop α5b-α6 in BsMiniIII is critical for specific dsRNA cleavage but not for dsRNA binding.

Conclusions:

• BsMiniIII represents a novel type of sequence-specific dsRNase.
• The enzyme's specificity is determined by a defined consensus sequence and its unique structural loop.
• BsMiniIII could serve as a prototype for developing tools for targeted dsRNA manipulation.