The S. cerevisiae SAGA complex functions in vivo as a coactivator for transcriptional activation by Gal4

Abstract

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.

Coactivators and general transcription factors have two distinct dynamic populations dependent on transcription

“…Studies in different eukaryotes have suggested that the presence of SAGA at the promoters of genes is needed to facilitate Pol II recruitment and pre‐initiation complex (PIC) formation (Wyce et al , 2007; Nagy et al , 2009; Helmlinger et al , 2011; Lang et al , 2011). The recruitment of SAGA and ATAC coactivator complexes to genomic loci has been suggested to take place by several distinct mechanisms: (i) by activator mediated recruitment (McMahon et al , 1998; Brown et al , 2001; Fishburn et al , 2005; Reeves & Hahn, 2005), (ii) by interactions with basal transcription machinery components (Larschan & Winston, 2001; Laprade et al , 2007; Mohibullah & Hahn, 2008) and (iii) through chromatin‐interacting domains of SAGA and ATAC subunits (Hassan et al , 2002; Vermeulen et al , 2010; Bian et al , 2011; Bonnet et al , 2014). Nevertheless, the dynamics of SAGA and ATAC interactions with chromatin are not yet well understood, as there has been no direct and systematic monitoring of the nuclear mobility of these two co‐activator complexes in live cells.…”

Actively Transcribed GAL Genes Can Be Physically Linked to the Nuclear Pore by the SAGA Chromatin Modifying Complex

“…The SAGA complex then facilitates recruitment of the general transcription factors and RNA polymerase II (27). As the SAGA complex regulates transcription of the GAL genes (23)(24)(25), and the GAL genes relocalize to the nuclear periphery upon transcriptional activation (5), we hypothesized that a physical interaction between Mlp proteins and the SAGA complex might mediate the recruitment of the GAL genes to the NPC. We verified the interaction between the Mlp proteins and SAGA components, and we found that both Mlp1 and Mlp2 interact with the GAL UAS, the region of the GAL genes that interacts with the SAGA complex.…”

“…With this approach, we identified three components of the evolutionarily conserved SAGA complex, a histone acetyltransferase complex that regulates transcription of ϳ10% of the yeast genome (21,22), including the GAL genes (23)(24)(25). SAGA interacts with genespecific transcriptional activators that recruit SAGA and additional transcription machinery to the promoters of target genes (26).…”

Effects of histone deacetylase inhibitors on transcriptional regulation of the hsp70 gene in Drosophila

“…Acetylation modification of histone affects the association of transcription factors with the their specific regulatory elements; reversely, the bound transcription factors may recruit the histone acetyltransferase to the promoter and to modify histones [7,32,33]. In this report, we demonstrated that HDI-induced histone hyperacetylation increased the binding affinity of HSF, but not that of GAF, to chromatin template (Figure 3).…”