The S. cerevisiae SAGA complex functions in vivo as a coactivator for transcriptional activation by Gal4.
Previous studies demonstrated that the SAGA (Spt-Ada-Gcn5-Acetyltransferase) complex facilitates the binding of TATA-binding protein (TBP) during transcriptional activation of the GAL1 gene of Saccharomyces cerevisiae. TBP binding was shown to require the SAGA components Spt3 and Spt20/Ada5, but not the SAGA component Gcn5. We have now examined whether SAGA is directly required as a coactivator in vivo by using chromatin immunoprecipitation analysis. Our results demonstrate that SAGA is physically recruited in vivo to the upstream activation sequence (UAS) regions of the galactose-inducible GAL genes. This recruitment is dependent on both induction by galactose and the Gal4 activation domain. Furthermore, we demonstrate that another well-characterized activator, Gal4-VP16, also recruits SAGA in vivo. Finally, we provide evidence that a specific interaction between Spt3 and TBP in vivo is important for Gal4 transcriptional activation at a step after SAGA recruitment. These results, taken together with previous studies, demonstrate a dependent pathway for the recruitment of TBP to GAL gene promoters consisting of the recruitment of SAGA by Gal4 and the subsequent recruitment of TBP by SAGA.
Larschan
E
E
Department of Genetics, Harvard Medical School, Boston, Massachusetts 02115, USA.
Winston
F
F
D000123:Acetyltransferases / Q000378:metabolism*; D002843:Chromatin / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D005656:Fungal Proteins / Q000235:genetics* / Q000378:metabolism*; D015966:Gene Expression Regulation, Fungal; D005800:Genes, Fungal; D005838:Genotype; D051548:Histone Acetyltransferases; D008954:Models, Biological; D016133:Polymerase Chain Reaction; D011401:Promoter Regions, Genetic; D011494:Protein Kinases / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins; D035181:TATA-Box Binding Protein; D015534:Trans-Activators / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism; D014158:Transcription, Genetic; D000099224:p300-CBP-Associated Factor
D000123:Acetyltransferases; D002843:Chromatin; D004268:DNA-Binding Proteins; D005656:Fungal Proteins; D051548:Histone Acetyltransferases; D011494:Protein Kinases; D029701:Saccharomyces cerevisiae Proteins; D035181:TATA-Box Binding Protein; D015534:Trans-Activators; D014157:Transcription Factors; C052130:GAL4 protein, S cerevisiae; C501392:GCN5 protein, S cerevisiae; D000099224:p300-CBP-Associated Factor