TFIIB-facilitated recruitment of preinitiation complexes by a TAF-independent mechanism.
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.
Department of Molecular Sciences, University of Tennessee Health Science Center, 858 Madison Avenue, Memphis, TN 38163, USA. rhori@utmem.edu
Roderick T
RT
Hori
Shuping
S
Xu
Xianyuan
X
Hu
Sung
S
Pyo
D019281:Dimerization; D017405:Herpes Simplex Virus Protein Vmw65 / Q000737:chemistry / Q000378:metabolism*; D046911:Macromolecular Substances; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D035381:TATA-Binding Protein Associated Factors / Q000378:metabolism*; D035581:Transcription Factor TFIIB / Q000378:metabolism*; D015533:Transcriptional Activation
D017405:Herpes Simplex Virus Protein Vmw65; D046911:Macromolecular Substances; D035381:TATA-Binding Protein Associated Factors; D035581:Transcription Factor TFIIB