Bidirectional DNA unwinding by a ternary complex of T antigen, nucleolin and topoisomerase I.
The simian virus 40 large tumour-antigen (T antigen) DNA helicase is a hexameric structure; it has been proposed that, in viral DNA replication, two of these hexamers are combined to form a bipartite holoenzyme that acts concurrently at both forks of a replication bubble. In a search for structural components of this helicase complex, we have identified nucleolin as a specific binding protein for the T-antigen hexamer. We show that nucleolin, in co-operation with human topoisomerase I, mediates the cohesion of the T-antigen helicase holoenzyme during plasmid unwinding. Our results provide biochemical evidence for a direct role of nucleolin in DNA replication, in addition to its known function in ribosome biogenesis. The data presented here suggest that nucleolin enables the formation of a functional 'helicase-swivelase' complex at the replication fork.
Seinsoth
Stephanie
S
Medizinische Biochemie und Molekularbiologie, Universität des Saarlandes, Gebaude 45, D-66421 Homburg, Germany.
Uhlmann-Schiffler
Heike
H
Stahl
Hans
H
D000595:Amino Acid Sequence; D000818:Animals; D000957:Antigens, Viral, Tumor / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D019556:COS Cells; D002460:Cell Line; D002522:Chlorocebus aethiops; D004247:DNA / Q000737:chemistry / Q000235:genetics* / Q000648:ultrastructure; D004265:DNA Helicases / Q000378:metabolism*; D004264:DNA Topoisomerases, Type I / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000378:metabolism; D010446:Peptide Fragments / Q000276:immunology; D010750:Phosphoproteins / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D013539:Simian virus 40 / Q000276:immunology; D018411:Spodoptera; D014162:Transfection; D000097796:Nucleolin
D000957:Antigens, Viral, Tumor; D004247:DNA; D004265:DNA Helicases; D004264:DNA Topoisomerases, Type I; D009687:Nuclear Proteins; D010446:Peptide Fragments; D010750:Phosphoproteins; D016601:RNA-Binding Proteins; D011994:Recombinant Proteins; D000097796:Nucleolin