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TAF-like function of SV40 large T antigen
1Department of Microbiology, School of Medicine, University of Pennsylvania, Philadelphia, 19104-6142, USA.
Genes & Development
|June 1, 1996
Summary
Simian virus 40 large T antigen activates promoters by acting like a TBP-associated factor (TAF). It rescues defects in TAF(II)250 and interacts with TFIID, suggesting a TAF-like function in transcription.
Area of Science:
- Molecular Biology
- Virology
- Gene Regulation
Background:
- Simian virus 40 (SV40) large T antigen (LT) activates simple promoters.
- LT's activation mechanism may involve interactions with basal transcription factors and upstream-bound factors.
- This mechanism resembles the function of TBP-associated factors (TAFs).
Purpose of the Study:
- To investigate whether SV40 large T antigen performs a TAF-like function in transcriptional activation.
- To elucidate the molecular interactions of large T antigen with components of the basal transcription machinery.
Main Methods:
- Genetic rescue experiments using the ts13 cell line with temperature-sensitive TAF(II)250.
- In vitro binding assays with Drosophila TAFs (dTAFs) and TBP.
- Coimmunoprecipitation experiments using SV40-infected cells expressing epitope-tagged TBP and antibodies against various TAFs and TBP.
Main Results:
- Large T antigen rescued the temperature-sensitive defect in TAF(II)250, unlike other viral proteins or LT mutants.
- Large T antigen demonstrated in vitro interactions with dTAFs and TBP.
- Large T antigen was coimmunoprecipitated with TFIID components (TBP, hTAFIIs) and copurified with TFIID from SV40-infected cells.
Conclusions:
- SV40 large T antigen exhibits TAF-like functions, augmenting or replacing TAF(II)250 activity.
- Large T antigen's transcriptional activation is mediated through its interaction with TFIID.
- These findings reveal a novel mechanism for viral protein-mediated transcriptional control via TAF mimicry.