title: Large T antigen on the simian virus 40 origin of replication: a 3D snapshot prior to DNA replication.
abstract: Large T antigen is the replicative helicase of simian virus 40. Its specific binding to the origin of replication and oligomerization into a double hexamer distorts and unwinds dsDNA. In viral replication, T antigen acts as a functional homolog of the eukaryotic minichromosome maintenance factor MCM. T antigen is also an oncoprotein involved in transformation through interaction with p53 and pRb. We obtained the three-dimensional structure of the full-length T antigen double hexamer assembled at its origin of replication by cryoelectron microscopy and single-particle reconstruction techniques. The double hexamer shows different degrees of bending along the DNA axis. The two hexamers are differentiated entities rotated relative to each other. Isolated strands of density, putatively assigned to ssDNA, protrude from the hexamer-hexamer junction mainly at two opposite sites. The structure of the T antigen at the origin of replication can be understood as a snapshot of the dynamic events leading to DNA unwinding. Based on these results a model for the initiation of simian virus 40 DNA replication is proposed.
authors.affiliation: Centro Nacional de Biotecnología, Campus Universidad Autónoma, 28049 Madrid, Spain.
authors.forename: Maria G
authors.initials: MG
authors.lastname: Gomez-Lorenzo
authors.forename: Mikel
authors.initials: M
authors.lastname: Valle
authors.forename: Joachim
authors.initials: J
authors.lastname: Frank
authors.forename: Claudia
authors.initials: C
authors.lastname: Gruss
authors.forename: Carlos Oscar S
authors.initials: CO
authors.lastname: Sorzano
authors.forename: Xiaojiang S
authors.initials: XS
authors.lastname: Chen
authors.forename: Luis Enrique
authors.initials: LE
authors.lastname: Donate
authors.forename: Jose Maria
authors.initials: JM
authors.lastname: Carazo
mesh_terms: D000465:Algorithms; D000957:Antigens, Viral, Tumor / Q000737:chemistry*; D001483:Base Sequence; D018360:Crystallography, X-Ray; D017931:DNA Primers; D004261:DNA Replication; D004279:DNA, Viral / Q000737:chemistry / Q000235:genetics*; D007091:Image Processing, Computer-Assisted; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction; D011487:Protein Conformation; D018741:Replication Origin / Q000235:genetics*; D013539:Simian virus 40 / Q000235:genetics / Q000276:immunology*
chemical_list: D000957:Antigens, Viral, Tumor; D017931:DNA Primers; D004279:DNA, Viral