Published online 22 July 2004
Nucleic Acids Research, Vol. 32 No. 13 © Oxford University Press 2004; all rights reserved
TFIIB-facilitated recruitment of preinitiation complexes by a TAF-independent mechanism
Department of Molecular Sciences, University of Tennessee Health Science Center, 858 Madison Avenue, Memphis, TN 38163, USA and 1 Department of Biological Chemistry, UCLA School of Medicine, 10833 LeConte Avenue, Los Angeles, CA 90095, USA
* To whom correspondence should be addressed. Tel: +1 901 448 6576; Fax: +1 901 448 7360; Email: rhori{at}utmem.edu
Present addresses: Shuping Xu, Department of Urology, University of Pittsburgh Medical Center, Pittsburgh, PA 15232, USA
Sung Pyo, Neo Diagnostics, Inc., 10532 Walker Street, Suite B, Cypress, CA 90630, USA
Received as resubmission May 18, 2004; Revised and Accepted June 30, 2004
Gene activators contain activation domains that are thought to recruit limiting components of the transcription machinery to a core promoter. VP16, a viral gene activator, has served as a model for studying the mechanistic aspects of transcriptional activation from yeast to human. The VP16 activation domain can be divided into two modules—an N-terminal subdomain (VPN) and a C-terminal subdomain (VPC). This study demonstrates that VPC stimulates core promoters that are either independent or dependent on TAFs (TATA-box Binding Protein-Associated Factors). In contrast, VPN only activates the TAF-independent core promoter and this activity increases in a synergistic fashion when VPN is dimerized (VPN2). Compared to one copy of VPN (VPN1), VPN2 also displays a highly cooperative increase in binding hTFIIB. The increased TFIIB binding correlates with VPN2's increased ability to recruit a complex containing TFIID, TFIIA and TFIIB. However, VPN1 and VPN2 do not increase the assembly of a complex containing only TFIID and TFIIA. The VPN subdomain also facilitates assembly of a complex containing TBP:TFIIA:TFIIB, which lacks TAFs, and provides a mechanism that could function at TAF-independent promoters. Taken together, these results suggest the interaction between VPN and TFIIB potentially initiate a network of contacts allowing the activator to indirectly tether TFIID or TBP to DNA.