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Self-assembly and condensation of intermolecular poly(UG) RNA quadruplexes
Saeed Roschdi1, Eric J Montemayor1, Rahul Vivek1
1Department of Biochemistry, University of Wisconsin-Madison, Madison, WI 53706, USA.
Poly(UG) repeats in RNA self-assemble into gel condensates via quadruplex (G4) interactions. These structures, crucial for gene silencing in C. elegans, exhibit diverse topologies and handedness based on sequence length.
Area of Science:
- Molecular Biology
- RNA Biology
- Biophysics
Background:
- Poly(UG) dinucleotide repeats are abundant in eukaryotic RNAs.
- In C. elegans, these repeats are added to RNA 3' ends for gene silencing within germ granule condensates.
- RNA structure and its role in cellular organization are key areas of research.
Purpose of the Study:
- To investigate the self-assembly properties of poly(UG) RNAs.
- To elucidate the structural basis of poly(UG) RNA condensates.
- To understand the role of quadruplex structures in RNA function.
Main Methods:
- RNA sequence analysis
- Gel electrophoresis and condensate formation assays
- High-resolution crystal structure determination (1.05 Å)
- Structural comparison of different poly(UG) RNA structures
Main Results:
- Poly(UG) RNAs self-assemble into gel condensates through quadruplex (G4) interactions.
- Short pUG sequences form right-handed intermolecular G4s, while longer sequences form left-handed intramolecular G4s.
- A high-resolution crystal structure revealed an eight-stranded G4 dimer with complex G and U quartet conformations, ions, and water.
Conclusions:
- Poly(UG) RNA sequences can form complex G4 structures with diverse topologies and handedness.
- G4 interactions are fundamental to the self-assembly of pUG RNAs into functional condensates.
- Understanding these structures provides insights into RNA-mediated gene silencing and cellular organization.
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