title: Positive and negative regulation of transcription in vitro: enhancer-binding protein AP-2 is inhibited by SV40 T antigen.
abstract: We have purified a 52 kd protein, AP-2, that binds to enhancer regions of SV40 and human metallothionein IIA (hMT IIA) and stimulates RNA synthesis from these promoters in vitro. Surprisingly, AP-2 also binds to two SV40 early promoter regions recognized by Sp1 and T antigen. Juxtaposed binding sites for AP-2 and Sp1 in the 21 bp repeats may facilitate productive interactions between the two factors. In contrast, sequence-specific binding of AP-2 to SV40 and hMT IIA DNA is inhibited by the viral repressor protein T antigen. Furthermore, T antigen inhibits AP-2-dependent transcriptional activation of the hMT IIA promoter in vitro. The inhibition is neither a direct nor an indirect result of T antigen binding to DNA, because the hMT IIA promoter lacks T antigen binding sites. Instead, sedimentation studies suggest that protein-protein interactions between AP-2 and T antigen block AP-2 binding to DNA. These findings suggest novel mechanisms for mediating positive and negative regulation of transcription.
mesh_terms: D000952:Antigens, Polyomavirus Transforming; D000957:Antigens, Viral, Tumor / Q000494:pharmacology*; D001483:Base Sequence; D001665:Binding Sites; D004279:DNA, Viral / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors / Q000302:isolation & purification* / Q000378:metabolism; D004742:Enhancer Elements, Genetic; D005786:Gene Expression Regulation; D005809:Genes, Regulator; D005814:Genes, Viral; D006801:Humans; D008668:Metallothionein / Q000235:genetics; D008957:Models, Genetic; D009856:Oncogene Proteins, Viral / Q000494:pharmacology*; D011401:Promoter Regions, Genetic; D011485:Protein Binding / Q000187:drug effects; D013539:Simian virus 40 / Q000235:genetics* / Q000276:immunology; D050656:Transcription Factor AP-2; D014157:Transcription Factors / Q000037:antagonists & inhibitors / Q000302:isolation & purification* / Q000378:metabolism; D014158:Transcription, Genetic / Q000187:drug effects
chemical_list: D000952:Antigens, Polyomavirus Transforming; D000957:Antigens, Viral, Tumor; D004279:DNA, Viral; D004268:DNA-Binding Proteins; D009856:Oncogene Proteins, Viral; D050656:Transcription Factor AP-2; D014157:Transcription Factors; D008668:Metallothionein