Abstract: |
The large tumor antigen (T antigen) specified by simian virus 40 (SV40) is required for viral DNA replication. To carry out its function, T antigen binds to duplex DNA at the origin of replication (oriSV40) and exerts a helicase activity that unwinds the two DNA strands. Previous work has defined two binding sites for T antigen near oriSV40, designated sites I and II; site II is within the 64-base-pair core sequence absolutely required for viral DNA replication. We have used electron microscopy and gel electrophoresis to characterize the interaction of T antigen with the origin region. We have found that effective binding to site II under conditions that support DNA replication requires ATP or a nonhydrolyzable analog. In the absence of ATP, T antigen binds mainly to site I; in the presence of ATP, both sites I and II are occupied, and binding is markedly increased. The ATP-dependent reaction generates a complex multimeric structure for T antigen. We conclude that T antigen forms an ATP-dependent nucleoprotein structure at oriSV40. We suggest that this nucleoprotein complex provides for the precise initiation of SV40 DNA replication. |
Keywords: |
dna binding protein; genetics; dna-binding proteins; methodology; dna replication; electron microscopy; metabolism; microscopy, electron; simian virus 40; binding site; dna, viral; binding sites; virus replication; adenosine triphosphate; virus t antigen; polyacrylamide gel electrophoresis; electrophoresis, polyacrylamide gel; virus dna; antigens, viral, tumor; nucleoprotein; nucleoproteins; article
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