Structural features of an Xrn1-resistant plant virus RNA

Area of Science:

• Molecular Biology
• Virology
• Biochemistry

Background:

• Xrn1 is a key 5'-3' exoribonuclease crucial for RNA metabolism in eukaryotes.
• RNA viruses can evade Xrn1 activity to regulate host RNA metabolism via subgenomic non-coding RNAs.
• A 'coremin' motif in the 3' untranslated region of some viruses is known to stall Xrn1, but its structure is poorly understood.

Purpose of the Study:

• To elucidate the structural features of the coremin motif responsible for Xrn1 stalling.
• To determine the minimal sequence and structural requirements for Xrn1 stalling by viral RNA.

Main Methods:

• In vitro Xrn1 degradation assays were performed.
• Over 50 RNA constructs based on the Beet necrotic yellow vein virus sequence were synthesized and tested.
• Structural features of RNA constructs were analyzed to identify elements critical for Xrn1 stalling.

Main Results:

• The minimal benyvirus Xrn1 stalling site comprises two essential hairpins: a 3-base pair hairpin with a YGAD consensus loop and a 4-base pair hairpin with a variable loop.
• A conserved 10-nucleotide spacer sequence between the hairpins may mediate tertiary interactions.
• Similar coremin motifs were identified in diverse plant virus families, including Betaflexiviridae, Virgaviridae, Potyviridae, and Secoviridae.

Conclusions:

• The coremin motif's minimal structure involves specific hairpin formations and loop sequences necessary for Xrn1 stalling.
• The identified structural features provide insight into viral RNA-protein interactions and Xrn1 regulation.
• Xrn1-stalling motifs are more prevalent across RNA viruses than previously recognized, suggesting a common viral strategy for manipulating host RNA decay pathways.