Structural dynamics in the La-module of La-related proteins

Area of Science:

• Molecular Biology
• Structural Biology
• Biochemistry

Background:

• La-related proteins (LaRPs) are crucial eukaryotic RNA-binding proteins involved in diverse cellular functions.
• Understanding LaRPs requires elucidating their RNA target selectivity, which is linked to distinct structural features.
• The conserved La-module is central to RNA recognition, but how it binds diverse RNA ligands remains unclear.

Purpose of the Study:

• Investigate the structural dynamics of human LaRP La-modules in relation to RNA recognition.
• Explore the architectural landscape and flexibility of LaRPs using biophysical methods.
• Determine how conserved La-modules achieve selectivity for diverse RNA targets.

Main Methods:

• Small Angle X-ray Scattering (SAXS) was used to study human LaRP La-modules.
• SAXS experiments were performed in both the absence (apo) and presence of RNA targets.
• Data were integrated with existing X-ray crystallography and NMR data.

Main Results:

• RNA binding generally induces compaction and reduces flexibility in the La-module.
• Significant differences in inherent flexibility were observed among apo LaRP La-modules.
• Each LaRP La-module exists in distinct conformational states (extended or compact) in equilibrium, varying between LaRPs.

Conclusions:

• Divergent flexibility and distinct conformational ensembles of LaRP La-modules are proposed to be critical for RNA substrate discrimination.
• These findings provide insights into the mechanistic basis of RNA target selectivity in the LaRP superfamily.
• The study highlights the dynamic nature of RNA-protein interactions in regulating gene expression.