title: Cellular topoisomerase I modulates origin binding by bovine papillomavirus type 1 E1.
abstract: In addition to viral proteins E1 and E2, bovine papillomavirus type 1 (BPV1) depends heavily on host replication machinery for genome duplication. It was previously shown that E1 binds to and recruits cellular replication proteins to the BPV1 origin of replication, including DNA polymerase alpha-primase, replication protein A (RPA), and more recently, human topoisomerase I (Topo I). Here, we show that Topo I specifically stimulates the origin binding of E1 severalfold but has no effect on nonorigin DNA binding. This is highly specific, as binding to nonorigin DNA is not stimulated, and other cellular proteins that bind E1, such as RPA and polymerase alpha-primase, show no such effect. The stimulation of E1's origin binding by Topo I is not synergistic with the stimulation by E2. Although the enhanced origin binding of E1 by Topo I requires ATP and Mg2+ for optimal efficiency, ATP hydrolysis is not required. Using an enzyme-linked immunosorbent assay, we showed that the interaction between E1 and Topo I is decreased in the presence of DNA. Our results suggest that Topo I participates in the initiation of papillomavirus DNA replication by enhancing E1 binding to the BPV1 origin.
authors.affiliation: Department of Microbiology and Immunology, University at Buffalo, The School of Medicine and Biomedical Sciences, 213 Biomedical Research Building, 3435 Main Street, Buffalo, New York 14214, USA.
authors.forename: Yan
authors.initials: Y
authors.lastname: Hu
authors.forename: Randolph V
authors.initials: RV
authors.lastname: Clower
authors.forename: Thomas
authors.initials: T
authors.lastname: Melendy
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology; D001665:Binding Sites; D002413:Cations, Divalent / Q000737:chemistry; D004264:DNA Topoisomerases, Type I / Q000378:metabolism*; D004279:DNA, Viral / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism*; D008274:Magnesium / Q000737:chemistry / Q000494:pharmacology; D011485:Protein Binding; D018741:Replication Origin / Q000235:genetics*; D013696:Temperature; D014764:Viral Proteins / Q000235:genetics* / Q000378:metabolism*
chemical_list: D002413:Cations, Divalent; D004279:DNA, Viral; D004268:DNA-Binding Proteins; C069814:E1 protein, Bovine papillomavirus; C051550:E2 protein, Bovine papillomavirus; D014764:Viral Proteins; D000255:Adenosine Triphosphate; D004264:DNA Topoisomerases, Type I; D008274:Magnesium