Structural basis of 3'-end poly(A) RNA recognition by LARP1

Area of Science:

• Molecular Biology
• Structural Biology
• Biochemistry

Background:

• La-related proteins (LARPs) are crucial RNA-binding proteins regulating gene expression.
• LARPs possess a conserved La-module (La motif and RNA recognition motif) for RNA binding.
• LARP1 is vital for ribosomal protein synthesis and mRNA stabilization, but its La-module structure was unknown.

Purpose of the Study:

• To structurally and functionally characterize the La-module of LARP1.
• To investigate the RNA binding specificity and mechanism of the LARP1 La-module.
• To elucidate the role of LARP1 RNA binding in cellular mRNA stabilization.

Main Methods:

• X-ray crystallography to determine high-resolution structures of the LARP1 La-module.
• Biochemical assays to assess poly(A) RNA binding affinity and specificity.
• Quantitative mRNA stabilization assays and poly(A) tail sequencing in cells.

Main Results:

• The LARP1 La-module lacks an RNA recognition motif (RRM) domain, differing from other LARPs.
• The La motif alone binds poly(A) RNA with submicromolar affinity and high specificity for the 3' end.
• Key residues (Q333, Y336, F348) in the La motif are critical for poly(A) RNA binding.
• LARP1 RNA binding is functionally relevant in cells, contributing to poly(A) 3' protection.

Conclusions:

• The LARP1 La-module exhibits unique structural features and RNA binding properties.
• LARP1's La motif is sufficient for specific poly(A) RNA recognition and stabilization.
• Structural insights into LARP1 RNA binding advance understanding of posttranscriptional regulation.