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Molecular and Cellular Biology, October 2001, p. 6882-6894, Vol. 21, No. 20
Laboratory of Biochemistry and Molecular
Biology, The Rockefeller University, New York, New York 10021
Received 27 April 2001/Returned for modification 5 June
2001/Accepted 12 July 2001
Human transcription factor TFIID contains the TATA-binding protein
(TBP) and several TBP-associated factors (TAFIIs). To
elucidate the structural organization and function of TFIID, we
expressed and characterized the product of a cloned cDNA encoding human TAFII135 (hTAFII135). Comparative far Western
blots have shown that hTAFII135 interacts strongly with
hTAFII20, moderately with hTAFII150, and weakly
with hTAFII43 and hTAFII250. Consistent with
these observations and with sequence relationships of
hTAFII20 and hTAFII135 to histones H2B and H2A,
respectively, TFIID preparations that contain higher levels of
hTAFII135 also contain higher levels of
hTAFII20, and the interaction between hTAFII20
and hTAFII135 is critical for human TFIID assembly in
vitro. From a functional standpoint, hTAFII135 has been
found to interact strongly and directly with hTFIIA and (within a
complex that also contains hTBP and hTAFII250) to
specifically cooperate with TFIIA to relieve TAFII250-mediated repression of TBP binding and function on
core promoters. Finally, we report a functional synergism between
TAFIIs and the TRAP/Mediator complex in activated
transcription, manifested as hTAFII-mediated inhibition of
basal transcription and a consequent TRAP requirement for both a
high absolute level of activated transcription and a high and more
physiological activated/basal transcription ratio. These results
suggest a dynamic TFIID structure in which the switch from a basal
hTAFII-enhanced repression state to an activator-mediated
activated state on a promoter may be mediated in part through activator
or coactivator interactions with hTAFII135.
0270-7306/01/$04.00+0 DOI: 10.1128/MCB.21.20.6882-6894.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Positive and Negative TAFII Functions That
Suggest a Dynamic TFIID Structure and Elicit Synergy with TRAPs in
Activator-Induced Transcription
*
Corresponding author. Mailing address: Laboratory of
Biochemistry and Molecular Biology, The Rockefeller University, 1230 York Ave., New York, NY 10021. Phone: (212) 327-7601. Fax: (212) 327-7949. E-mail: roeder{at}rockvax.rockefeller.edu.
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