Probing sequence-specific RNA recognition by the bacteriophage MS2 coat protein

Area of Science:

• Molecular Biology
• Structural Biology
• Biochemistry

Background:

• The MS2 RNA translational operator (TR) is a key regulatory element in viral gene expression.
• Understanding RNA-protein interactions is crucial for molecular biology and drug development.
• Previous X-ray crystallography studies have provided structural insights into MS2 phage capsids.

Purpose of the Study:

• To define the essential recognition elements on the MS2 RNA translational operator (TR) for coat protein complex formation.
• To investigate the role of specific nucleotide modifications in RNA-protein binding affinity.
• To compare in vitro binding in solution with complexes formed with phage capsids.

Main Methods:

• In vitro binding studies using chemically synthesized RNA operators with modified functional groups.
• Modification-binding interference assays.
• Comparison of binding data with existing X-ray crystallographic structures of MS2 phage capsids.

Main Results:

• Key nucleotide positions and functional groups essential for MS2 coat protein recognition were identified.
• Complex formation between TR and RNA-free phage capsids is identical to that between TR and a single coat protein dimer in solution.
• Operator affinity is influenced by factors beyond direct RNA-protein contacts, suggesting conformational changes in the unliganded operator.

Conclusions:

• Specific modifications on the MS2 RNA operator precisely define its interaction with the coat protein.
• The binding mode of the MS2 RNA operator is conserved whether interacting with a single coat protein dimer or within a phage capsid.
• Modified oligoribonucleotides are a valuable tool for dissecting complex RNA-ligand interactions.