title: Model for T-antigen-dependent melting of the simian virus 40 core origin based on studies of the interaction of the beta-hairpin with DNA.
abstract: The interaction of simian virus 40 (SV40) T antigen (T-ag) with the viral origin has served as a model for studies of site-specific recognition of a eukaryotic replication origin and the mechanism of DNA unwinding. These studies have revealed that a motif termed the "beta-hairpin" is necessary for assembly of T-ag on the SV40 origin. Herein it is demonstrated that residues at the tip of the "beta-hairpin" are needed to melt the origin-flanking regions and that the T-ag helicase domain selectively assembles around one of the newly generated single strands in a manner that accounts for its 3'-to-5' helicase activity. Furthermore, T-ags mutated at the tip of the "beta-hairpin" are defective for oligomerization on duplex DNA; however, they can assemble on hybrid duplex DNA or single-stranded DNA (ssDNA) substrates provided the strand containing the 3' extension is present. Collectively, these experiments indicate that residues at the tip of the beta-hairpin generate ssDNA in the core origin and that the ssDNA is essential for subsequent oligomerization events.
authors.affiliation: Department of Biochemistry A703, Tufts University School of Medicine, 136 Harrison Avenue, Boston, MA 02111, USA.
authors.forename: Anuradha
authors.initials: A
authors.lastname: Kumar
authors.forename: Gretchen
authors.initials: G
authors.lastname: Meinke
authors.forename: Danielle K
authors.initials: DK
authors.lastname: Reese
authors.forename: Stephanie
authors.initials: S
authors.lastname: Moine
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Phelan
authors.forename: Amélie
authors.initials: A
authors.lastname: Fradet-Turcotte
authors.forename: Jacques
authors.initials: J
authors.lastname: Archambault
authors.forename: Andrew
authors.initials: A
authors.lastname: Bohm
authors.forename: Peter A
authors.initials: PA
authors.lastname: Bullock
mesh_terms: D020816:Amino Acid Motifs / Q000235:genetics; D000957:Antigens, Viral, Tumor / Q000235:genetics / Q000378:metabolism*; D004265:DNA Helicases / Q000235:genetics / Q000378:metabolism*; D004261:DNA Replication / Q000235:genetics / Q000502:physiology*; D004277:DNA, Single-Stranded / Q000235:genetics / Q000378:metabolism*; D008958:Models, Molecular; D009154:Mutation / Q000235:genetics; D009841:Oligonucleotides; D018741:Replication Origin / Q000235:genetics*; D013539:Simian virus 40 / Q000235:genetics / Q000378:metabolism*; D014779:Virus Replication
chemical_list: D000957:Antigens, Viral, Tumor; D004277:DNA, Single-Stranded; D009841:Oligonucleotides; D004265:DNA Helicases