Bidirectional DNA unwinding by a ternary complex of T antigen,nucleolin and topoisomerase I |
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Authors: | Seinsoth Stephanie Uhlmann-Schiffler Heike Stahl Hans |
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Institution: | Medizinische Biochemie und Molekularbiologie, Universit?t des Saarlandes, Gebaude 45, D-66421 Homburg, Germany. |
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Abstract: | 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. |
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