title: SV40 gene expression is modulated by the cooperative binding of T antigen to DNA.
abstract: We analyzed the DNA binding properties of wild-type simian virus 40 large T antigen and found that the protein binds cooperatively to three tandem sites at a regulatory region of SV40 DNA. One consequence of this T antigen:DNA interaction is the specific repression of SV40 early RNA synthesis in vitro. We mapped a region of 85 base pairs that is necessary and sufficient to initiate early SV40 transcription in vitro. This promoter region lies directly adjacent to the third T antigen binding site but does not include that "TATA" sequence. To determine how T antigen interacts with its binding sites to repress RNA synthesis, we analyzed transcription directed by a variety of wild-type, mutant and hybrid template DNAs. Our findings suggest that the cooperative binding of T antigen to its sites is directly responsible for inhibiting the initiation, rather than blocking elongation, of early RNA synthesis. A model is presented to explain the role of T antigen binding in the regulation of viral transcription and DNA replication during SV40 lytic infection.
mesh_terms: D000951:Antigens, Neoplasm; D000956:Antigens, Viral; D000957:Antigens, Viral, Tumor; D001483:Base Sequence; D001665:Binding Sites; D004261:DNA Replication; D004279:DNA, Viral / Q000378:metabolism*; D005786:Gene Expression Regulation; D008957:Models, Genetic; D009876:Operon; D012367:RNA, Viral / Q000096:biosynthesis; D013539:Simian virus 40 / Q000235:genetics* / Q000276:immunology; D014158:Transcription, Genetic; D014779:Virus Replication
chemical_list: D000951:Antigens, Neoplasm; D000956:Antigens, Viral; D000957:Antigens, Viral, Tumor; D004279:DNA, Viral; D012367:RNA, Viral