Modulation of the Herpes Simplex Virus Type-1 UL9 DNA Helicase by Its Cognate Single-strand DNA-binding Protein, ICP8

Mercedes E. Arana, Bushra Haq, Nicolas Tanguy Le Gac, Paul E. Boehmer

Research output: Contribution to journalArticlepeer-review

17 Scopus citations


The mechanism of stimulation of a DNA helicase by its cognate single-strand DNA-binding protein was examined using herpes simplex virus type-1 UL9 DNA helicase and ICP8. UL9 and ICP8 are two essential components of the viral replisome that associate into a complex to unwind the origins of replication. The helicase and DNA-stimulated ATPase activities of UL9 are greatly elevated as a consequence of this association. Given that ICP8 acts as a single-strand DNA-binding protein, the simplest model that can account for its stimulatory effect predicts that it tethers UL9 to the DNA template, thereby increasing its processivity. In contrast to the prediction, data presented here show that the stimulatory activity of ICP8 does not depend on its single-strand DNA binding activity. Our data support an alternative hypothesis in which ICP8 modulates the activity of UL9. Accordingly, the data show that the ICP8-binding site of UL9 constitutes an inhibitory region that maintains the helicase in an inefficient ground state. ICP8 acts as a positive regulator by neutralizing this region. ICP8 does not affect substrate binding, ATP hydrolysis, or the efficiency of translocation/DNA unwinding. Rather, we propose that ICP8 increases the efficiency with which substrate binding and ATP hydrolysis are coupled to translocation/DNA unwinding.

Original languageEnglish (US)
Pages (from-to)6840-6845
Number of pages6
JournalJournal of Biological Chemistry
Issue number9
StatePublished - Mar 2 2001
Externally publishedYes

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology


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