title: Sequence independent duplex DNA opening reaction catalysed by SV40 large tumor antigen.
abstract: Simian virus 40 (SV40) large tumor antigen (T antigen) is mainly localized in the nucleus where it exhibits two biochemical properties: DNA binding and helicase activity. Both activities are necessary for viral DNA replication and may also enable T antigen to modulate cellular growth. Here we present biochemical and electron microscopic evidence that the helicase activity can start at internal sites of fully double-stranded DNA molecules not containing the SV40 origin or replication. Using T antigen specific monoclonal antibodies, this unwinding reaction can be biochemically divided in an initiation (duplex opening) and a propagation step. The duplex opening reaction (as well as the propagation step) does not depend on a specific DNA sequence or secondary structure. In addition, we have found that T antigen forms an ATP dependent nucleoprotein complex at double-stranded DNA, which may be an essential step for the sequence independent duplex DNA opening reaction.
authors.affiliation: Fakultät für Biologie, Universität Konstanz, FRG.
authors.forename: M
authors.initials: M
authors.lastname: Scheffner
authors.forename: R
authors.initials: R
authors.lastname: Wessel
authors.forename: H
authors.initials: H
authors.lastname: Stahl
mesh_terms: D000911:Antibodies, Monoclonal; D000952:Antigens, Polyomavirus Transforming / Q000235:genetics*; D002460:Cell Line; D004279:DNA, Viral / Q000235:genetics* / Q000648:ultrastructure; D004268:DNA-Binding Proteins; D008854:Microscopy, Electron; D013539:Simian virus 40 / Q000235:genetics*
chemical_list: D000911:Antibodies, Monoclonal; D000952:Antigens, Polyomavirus Transforming; D004279:DNA, Viral; D004268:DNA-Binding Proteins