Download MendeleyThe crystal structure of the herpes virus ICP8 protein in complex with single-stranded DNA reveals the molecular determinants of nucleotide recognition.
Erlandsen, H., Krucinska, J., Wilderman, P.R., Makkay, A.M., Szczepaniak, R., Wright, L.R., Weller, S.K., Wright, D.L.(2026) J Biological Chem : 111366-111366
- PubMed: 41833734 Search on PubMed
- DOI: https://doi.org/10.1016/j.jbc.2026.111366
- Primary Citation Related Structures:
9PI3, 9PI4, 9PI5, 9PI6 - PubMed Abstract:
The HSV-1 single-strand annealing protein ICP8 (UL29) is essential for viral DNA replication and recombination. Although its overall architecture has been described, the molecular basis of single-stranded DNA (ssDNA) recognition was unknown. We report crystal structures of C-terminally truncated ICP8 (ICP8Δ60) bound to poly(dT)25 or poly(dA)25 ssDNA at 3.0-3.1 Å resolution, along with higher-resolution apo structures of surface-entropy-reduction variants. ssDNA binds within the neck region between the head and shoulder domains, contacting conserved OB-fold residues via base-specific hydrogen bonds, π-stacking and phosphate backbone interactions. In the poly(dT)25 complex, coordination of a Zn 2+ ion stabilizes the zinc finger motif; whereas, in the poly(dA)25 complex, Zn 2+ displacement promotes disulfide bond formation that effectively locks the protein into an altered conformation. Microscale thermophoresis and label-free differential scanning fluorimetry reveal a strong preference for pyrimidine-rich sequences, with nanomolar affinity for poly(dT)25 and micromolar for poly(dA)25. Structural modeling identified Y543, R576, R772, R793, Y988, and F998 as key DNA-contact residues. Alanine substitutions caused severe replication defects, particularly for R772A, Y988A, and F998A. ssDNA binding induces ∼26 Å displacement and ∼35 degree rotation of the C-terminal domain and ordering of flexible loops, suggesting a mechanism for cooperative filament assembly. These structures define the molecular determinants of ICP8-ssDNA recognition, reveal thymidine bias and provide a framework for targeting ICP8-mediated functions in herpesvirus replication.
- University of Connecticut School of Pharmacy, Storrs, CT, USA, 06269.
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