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J. Virol., Feb 1996, 1191-1202, Vol 70, No. 2
SD Johnston, XM Yu and JE Mertz
Simian virus 40 (SV40) large T antigen (Tag) is a promiscuous
transcriptional transactivator; however, its mechanism of transactivation
remains unknown. Recent studies have suggested the possible involvement of
protein-protein interactions with TBP, the TATA box-binding protein of
TFIID, and TEF-1, an enhancer-binding factor. We show here that (i) the Tag
domain containing amino acids 133 to 249 directly interacts with the
general transcription factor TFIIB, the activator protein Sp1, and the
140-kDa subunit of RNA polymerase II, as well as with TBP and TEF-1; (ii)
these interactions can also occur when these transcription factors are
present in their functional states in cellular extracts; (iii) binding of
Tag to TBP is eliminated by preincubation of TBP either at 48 degrees C or
with the adenovirus 13S E1a protein; (iv) this domain of Tag cannot bind
concurrently to more than one of these transcription factors; and (v) the
substitution of Tag amino acid residues 173 and 174 inactivates the ability
of this Tag domain both to associate with any of these transcription
factors and to transactivate the SV40 late promoter. Thus, we conclude that
SV40 Tag probably does not transactivate via the concurrent interaction
with multiple components of the preinitiation complex. Rather, we
hypothesize that transactivation by Tag may primarily occur by removing or
preventing the binding of factors that inhibit the formation of
preinitiation complexes.
Copyright © 1996, American Society for Microbiology
The major transcriptional transactivation domain of simian virus 40 large T antigen associates nonconcurrently with multiple components of the transcriptional preinitiation complex
McArdle Laboratory for Cancer Research, University of Wisconsin, Medical School, Madison 53706-1599, USA.
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