Positive and negative regulation of transcription in vitro: Enhancer-binding protein AP-2 is inhibited by SV40 T antigen

Pamela J. Mitchell, Charlotte Wang, Robert Tjian

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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.

Original languageEnglish (US)
Pages (from-to)847-861
Number of pages15
Issue number6
StatePublished - Sep 11 1987


All Science Journal Classification (ASJC) codes

  • Biochemistry, Genetics and Molecular Biology(all)

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