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.
Hori
Roderick T
RT
Department of Molecular Sciences, University of Tennessee Health Science Center, 858 Madison Avenue, Memphis, TN 38163, USA. rhori@utmem.edu
Xu
Shuping
S
Hu
Xianyuan
X
Pyo
Sung
S
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