The crystal structure of the herpes virus ICP8 protein in complex with single-stranded DNA reveals the molecular determinants of nucleotide recognition.
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| Title: | The crystal structure of the herpes virus ICP8 protein in complex with single-stranded DNA reveals the molecular determinants of nucleotide recognition. |
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| Authors: | Erlandsen, Heidi1, Krucinska, Jolanta1, Wilderman, P. Ross2, Makkay, Andrea M.2, Szczepaniak, Renata2, Wright, Lee R.1, Weller, Sandra K.2 Weller@UCHC.edu, Wright, Dennis L.1 Dennis.Wright@UConn.edu |
| Source: | Journal of Biological Chemistry. May2026, Vol. 302 Issue 5, p1-20. 20p. |
| Subjects: | Single-stranded DNA, DNA-protein interactions, DNA replication, Zinc-finger proteins, DNA-binding proteins, Crystal structure, Herpesviruses |
| 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 to 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 basespecific hydrogen bonds, π-stacking and phosphate backbone interactions. In the poly(dT)25 complex, coordination of a Zn2+ ion stabilizes the zinc finger motif; whereas, in the poly(dA)25 complex, Zn2+ 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. [ABSTRACT FROM AUTHOR] |
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| Database: | Engineering Source |
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