title: Direct interaction between the N- and C-terminal portions of the herpes simplex virus type 1 origin binding protein UL9 implies the formation of a head-to-tail dimer.
abstract: UL9, a superfamily II helicase, is a multifunctional protein required for herpes simplex virus type 1 replication in vivo. Although the C-terminal 317-amino-acid DNA binding domain of UL9 exists as a monomer, the full-length protein behaves as a dimer in solution. Thus, it has been assumed that the N-terminal 534 residues contain a region necessary for efficient dimerization and that UL9 dimers are in a head-to-head configuration. We recently showed, however, that residues in the N terminus could modulate the inhibitory properties of UL9 by decreasing the DNA binding ability of the C terminus (S. Chattopadhyay and S. K. Weller, J. Virol. 80:4491-4500, 2006). We suggested that a direct interaction between the N- and C-terminal portions of UL9 might exist and serve to modulate the DNA binding activities of the C terminus. In this study, we used a coimmunoprecipitation assay to show that the N-terminal portion of UL9 can indeed directly interact with the C terminus. A series of truncation mutant proteins were used to show that a region in the N terminus between residues 293 and 321 is necessary for efficient interaction. Similarly, a region in the C terminus between residues 600 and 800 is required for this interaction. The simplest model to explain these data is that UL9 dimers are oriented in a head-to-tail arrangement in which the N terminus is in contact with the C terminus.
authors.affiliation: Department of Molecular, Microbial, and Structural Biology, MC3205, University of Connecticut Health Center, 263 Farmington Avenue, Farmington, CT 06030, USA.
authors.forename: Soma
authors.initials: S
authors.lastname: Chattopadhyay
authors.forename: Sandra K
authors.initials: SK
authors.lastname: Weller
mesh_terms: D000818:Animals; D016367:Baculoviridae; D002478:Cells, Cultured; D002522:Chlorocebus aethiops; D004265:DNA Helicases; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D019281:Dimerization; D018259:Herpesvirus 1, Human / Q000737:chemistry / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D006801:Humans; D047468:Immunoprecipitation; D008856:Microscopy, Fluorescence; D009154:Mutation; D010957:Plasmids; D018411:Spodoptera; D014162:Transfection; D014709:Vero Cells; D014764:Viral Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure
chemical_list: D004268:DNA-Binding Proteins; D014764:Viral Proteins; C064565:UL9 protein, Human herpesvirus 1; D004265:DNA Helicases