Duplex destabilization by four ribosomal DEAD-box proteins

Area of Science:

• Molecular Biology
• Biochemistry
• RNA Biology

Background:

• DEAD-box proteins are crucial for RNA folding by destabilizing RNA structures.
• The mechanism linking ATP hydrolysis to helix destabilization varies among DEAD-box proteins.

Purpose of the Study:

• Investigate the helix-disrupting abilities of four yeast ribosomal DEAD-box proteins: Dbp3p, Dbp4p, Rok1p, and Rrp3p.
• Determine how ATP hydrolysis is coupled to RNA unwinding by these proteins.

Main Methods:

• Assayed four Saccharomyces cerevisiae DEAD-box proteins using RNA substrates with duplex and single-stranded regions.
• Utilized ATP, AMPPNP, and ADP to study nucleotide-dependent unwinding and displacement activities.

Main Results:

• All four proteins unwound a 10 bp helix in vitro with ATP; longer helices were not significantly dissociated.
• Dbp3p unwound helices without extensions, while Dbp4p, Rok1p, and Rrp3p required 5' or 3' single-stranded extensions.
• A length-dependent preference for 3' extensions was observed for Dbp4p, Rok1p, and Rrp3p, suggesting substrate orientation.
• Nucleotide binding (AMPPNP or ADP) was sufficient for duplex disruption by all four proteins.
• Dbp3p and Rrp3p showed enhanced strand displacement rates with ATP.

Conclusions:

• Yeast ribosomal DEAD-box proteins possess RNA unwinding capabilities.
• The requirement for single-stranded extensions and directional binding varies among these DEAD-box proteins.
• Nucleotide binding alone can facilitate duplex disruption, while ATP hydrolysis provides further enhancement for specific proteins.