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.
Publication types
-
Research Support, Non-U.S. Gov't
-
Research Support, U.S. Gov't, P.H.S.
MeSH terms
-
Antigens, Polyomavirus Transforming
-
Antigens, Viral, Tumor / pharmacology*
-
Base Sequence
-
Binding Sites
-
DNA, Viral / genetics
-
DNA, Viral / metabolism
-
DNA-Binding Proteins / antagonists & inhibitors
-
DNA-Binding Proteins / isolation & purification*
-
DNA-Binding Proteins / metabolism
-
Enhancer Elements, Genetic*
-
Gene Expression Regulation*
-
Genes, Regulator*
-
Genes, Viral
-
Humans
-
Metallothionein / genetics
-
Models, Genetic
-
Oncogene Proteins, Viral / pharmacology*
-
Promoter Regions, Genetic
-
Protein Binding / drug effects
-
Simian virus 40 / genetics*
-
Simian virus 40 / immunology
-
Transcription Factor AP-2
-
Transcription Factors / antagonists & inhibitors
-
Transcription Factors / isolation & purification*
-
Transcription Factors / metabolism
-
Transcription, Genetic / drug effects
Substances
-
Antigens, Polyomavirus Transforming
-
Antigens, Viral, Tumor
-
DNA, Viral
-
DNA-Binding Proteins
-
Oncogene Proteins, Viral
-
Transcription Factor AP-2
-
Transcription Factors
-
Metallothionein