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A structurally conserved motif in γ-herpesvirus uracil-DNA glycosylases elicits duplex nucleotide-flipping

DOI: 10.1093/nar/gky217 DOI Help

Authors: Christopher Earl (University of London) , Claire Bagneris (Birkbeck College) , Kara Zeman (University of London) , Ambrose Cole (Institute of Structural and Molecular Biology, Birkbeck College, University of London) , Tracey Barrett (Institute of Structural and Molecular Biology, Birkbeck College, University of London) , Renos Savva (Institute of Structural and Molecular Biology, Birkbeck College, University of London)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Nucleic Acids Research , VOL 332

State: Published (Approved)
Published: March 2018
Diamond Proposal Number(s): 9204 , 12305 , 17201

Open Access Open Access

Abstract: Efficient γ-herpesvirus lytic phase replication requires a virally encoded UNG-type uracil-DNA glycosylase as a structural element of the viral replisome. Uniquely, γ-herpesvirus UNGs carry a seven or eight residue insertion of variable sequence in the otherwise highly conserved minor-groove DNA binding loop. In Epstein–Barr Virus [HHV-4] UNG, this motif forms a disc-shaped loop structure of unclear significance. To ascertain the biological role of the loop insertion, we determined the crystal structure of Kaposi’s sarcoma-associated herpesvirus [HHV-8] UNG (kUNG) in its product complex with a uracil-containing dsDNA, as well as two structures of kUNG in its apo state. We find the disc-like conformation is conserved, but only when the kUNG DNA-binding cleft is occupied. Surprisingly, kUNG uses this structure to flip the orphaned partner base of the substrate deoxyuridine out of the DNA duplex while retaining canonical UNG deoxyuridine-flipping and catalysis. The orphan base is stably posed in the DNA major groove which, due to DNA backbone manipulation by kUNG, is more open than in other UNG–dsDNA structures. Mutagenesis suggests a model in which the kUNG loop is pinned outside the DNA-binding cleft until DNA docking promotes rigid structuring of the loop and duplex nucleotide flipping, a novel observation for UNGs.

Subject Areas: Biology and Bio-materials


Instruments: I04-Macromolecular Crystallography

Added On: 05/04/2018 11:42

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