Open AccessModel for T-Antigen-Dependent Melting of the Simian Virus 40 Core Origin Based on Studies of the Interaction of the Beta-Hairpin with DNA
Author(s) -
Anuradha Kumar,
Gretchen Meinke,
Danielle K. Reese,
Stephanie Moine,
Paul Phelan,
Amélie Fradet-Turcotte,
Jacques Archambault,
Andrew Bohm,
Peter A. Bullock
Publication year - 2007
Publication title -
journal of virology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.617
H-Index - 292
eISSN - 1070-6321
pISSN - 0022-538X
DOI - 10.1128/jvi.02451-06
Subject(s) - biology , helicase , dna , duplex (building) , prokaryotic dna replication , microbiology and biotechnology , dna replication , origin of replication , biophysics , virology , rna , genetics , gene
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.