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The E2 trans-activator can act as a repressor by interfering with a cellular transcription factor
1Department of Molecular Biology, University of California, Berkeley 94720.
Genes & Development
|January 1, 1990
Summary
The bovine papillomavirus E2 protein can act as both a transcriptional activator and repressor. Its function depends on its binding site location, similar to prokaryotic systems, influencing gene expression.
Area of Science:
- Molecular Biology
- Virology
- Genetics
Background:
- The E2 open reading frame (ORF) of bovine papillomavirus (BPV-1) encodes site-specific DNA-binding proteins.
- Full-length E2 protein functions as a transcriptional activator, while carboxy-terminal domains act as repressors.
Purpose of the Study:
- To investigate the dual role of the BPV-1 E2 trans-activator as a repressor.
- To identify the DNA sequence and binding site requirements for E2-mediated repression.
Main Methods:
- Analysis of BPV-1 promoter activity.
- Site-directed mutagenesis and DNA-binding assays.
- DNase footprinting assays using HeLa cell extracts.
Main Results:
- The E2 trans-activator represses transcription of a BPV-1 promoter by binding to a 12-bp operator site downstream of the cap site.
- This operator site is crucial for basal promoter activity and is protected in DNase footprint assays.
- Repression is not due to blocking RNA polymerase, as altering the binding site position negates the repressive effect.
Conclusions:
- The BPV-1 E2 protein exhibits context-dependent function, acting as either an activator or repressor.
- The precise location of the E2 binding site relative to promoter elements determines its regulatory effect.
- This regulatory mechanism parallels findings in prokaryotic systems, highlighting conserved principles in gene regulation.