Analysis of TFIIA Function In Vivo: Evidence for a Role in TATA-Binding Protein Recruitment and Gene-Specific Activation
| Autor: | Scott E. Gabriel, Kelli L. Roinick, Karen M. Arndt, Qing Liu, Robert D. Ward |
|---|---|
| Rok vydání: | 1999 |
| Předmět: |
Transcriptional Activation
Saccharomyces cerevisiae Proteins TATA box Genes Fungal Gene Expression Saccharomyces cerevisiae Fungal Proteins Transcription (biology) Promoter Regions Genetic Molecular Biology RNA polymerase II holoenzyme Transcriptional Regulation Genetics biology Cell Biology TATA-Box Binding Protein Cell biology DNA-Binding Proteins Phenotype Mutagenesis Transcription Factor TFIIA Transcription preinitiation complex biology.protein Transcription factor II D TATA-binding protein Transcription factor II B Transcription factor II A Transcription Factors |
| Zdroj: | Molecular and Cellular Biology. 19:8673-8685 |
| ISSN: | 1098-5549 |
| DOI: | 10.1128/mcb.19.12.8673 |
| Popis: | Activation of transcription can occur by the facilitated recruitment of TFIID to promoters by gene-specific activators. To investigate the role of TFIIA in TFIID recruitment in vivo, we exploited a class of yeast TATA-binding protein (TBP) mutants that is activation and DNA binding defective. We found that cooverexpression of TOA1 and TOA2, the genes that encode yeast TFIIA, overcomes the activation defects caused by the TBP mutants. Using a genetic screen, we isolated a new class of TFIIA mutants and identified three regions on TFIIA that are likely to be involved in TBP recruitment or stabilization of the TBP-TATA complex in vivo. Amino acid replacements in only one of these regions enhance TFIIA-TBP-DNA complex formation in vitro, suggesting that the other regions are involved in regulatory interactions. To determine the relative importance of TFIIA in the regulation of different genes, we constructed yeast strains to conditionally deplete TFIIA levels prior to gene activation. While the activation of certain genes, such as INO1, was dramatically impaired by TFIIA depletion, activation of other genes, such as CUP1, was unaffected. These data suggest that TFIIA facilitates DNA binding by TBP in vivo, that TFIIA may be regulated by factors that target distinct regions of the protein, and that promoters vary significantly in the degree to which they require TFIIA for activation. Initiation of mRNA synthesis in eukaryotes depends upon the controlled and coordinated activities of a large number of proteins. RNA polymerase II and six different general transcription factors (TFIIA, TFIIB, TFIID, TFIIE, TFIIF, and TFIIH) assemble into a transcriptionally competent preinitiation complex (PIC) at the core promoter elements of class II genes (47). Among the general transcription factors, TFIID plays a central role in initiation as it binds specifically to the TATA box through its component TATA-binding protein (TBP) and nucleates PIC assembly (47). Gene-specific transcriptional regulators typically bind upstream of the TATA box and, in concert with coactivators and corepressors, modulate the level of initiation by affecting the assembly or activity of the PIC. Although any step in the initiation reaction potentially may be regulated by the gene-specific factors, a growing body of data suggests that some transcriptional activators enhance the rate of initiation by recruiting TFIID to the core promoter or by recruiting the RNA polymerase II holoenzyme to the nascent PIC (20, 54, 65). |
| Databáze: | OpenAIRE |
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