Article

Grant PA, Duggan L, Côté J, Roberts SM, Brownell JE, Candau R et al.. Yeast Gcn5 functions in two multisubunit complexes to acetylate nucleosomal histones: characterization of an Ada complex and the SAGA (Spt/Ada) complex. Genes Dev 11: 1640-1650

Harvard University, Cambridge, Massachusetts, United States
Genes & Development (Impact Factor: 10.8). 08/1997; 11(13):1640-50. DOI: 10.1101/gad.11.13.1640
Source: PubMed

ABSTRACT

The transcriptional adaptor protein Gcn5 has been identified as a nuclear histone acetyltransferase (HAT). Although recombinant yeast Gcn5 efficiently acetylates free histones, it fails to acetylate histones contained in nucleosomes, indicating that additional components are required for acetylation of chromosomal histones. We report here that Gcn5 functions as a catalytic subunit in two high-molecular-mass native HAT complexes, with apparent molecular masses of 0.8 and 1.8 megadalton (MD), respectively, which acetylate nucleosomal histones. Both the 0.8- and 1.8-MD Gcn5-containing complexes cofractionate with Ada2 and are lost in gcn5delta, ada2delta, or ada3delta yeast strains, illustrating that these HAT complexes are bona fide native Ada-transcriptional adaptor complexes. Importantly, the 1.8-MD adaptor/HAT complex also contains Spt gene products that are linked to TATA-binding protein (TBP) function. This complex is lost in spt20/ada5delta and spt7delta strains and Spt3, Spt7, Spt20/Ada5, Ada2, and Gcn5 all copurify with this nucleosomal HAT complex. Therefore, the 1.8-MD adaptor/HAT complex illustrates an interaction between Ada and Spt gene products and confirms the existence of a complex containing the TBP group of Spt proteins as demonstrated by genetic and biochemical studies. We have named this novel transcription regulatory complex SAGA (Spt-Ada-Gcn5-Acetyltransferase). The function of Gcn5 as a histone acetyltransferase within the Ada and SAGA adaptor complexes indicates the importance of histone acetylation during steps in transcription activation mediated by interactions with transcription activators and general transcription factors (i.e., TBP).

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    • "This complex is generally regarded as a coactivator complex (Kuo et al., 1998), but also has a negative role in gene expression (Belotserkovskaya et al., 2000; Ricci et al., 2002). The SAGA complex is involved in histone acetylation (HAT) (Grant et al., 1997), histone deubiquitination (Daniel et al., 2004), mRNA export (Rodríguez-Navarro et al., 2004), transcription elongation (Govind et al., 2007), chromatin recognition (Pray-Grant et al., 2005), and regulation of the basal transcription machinery (Sterner et al., 1999). Unraveling the modular composition of the SAGA complex has enabled interpretation of its multifunctional role (Wu et al., 2004), principally in regulating the transcription of many stress-inducible (Huisinga and Pugh, 2004) and developmentally regulated genes (reviewed in Wang and Dent, 2014). "
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    • "SGF29 is a subunit of SAGA (Sanders et al. 2002), a large chromatin-modifying complex that regulates gene expression. SAGA is evolutionarily conserved and was initially identified in budding yeast where it was shown to acetylate and deubiquitylate histones (Fig. 3.1a) (Grant et al. 1997; Lee and Workman 2007). The SGF29 subunit is required for the recruitment of SAGA to gene promoters and for the acetylation of histone H3 by SAGA (Bian et al. 2011). "
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    • "The Gcn5 HAT is found within different complexes in vivo; namely, ADA/HAT-A2, SAGA, SLIK, and ATAC (Steunou et al. 2014). Recombinant yGcn5 enzyme mainly acetylates H3 and, to a lesser extent, H4 in free histones but is unable to target nucleosomes (Kuo et al. 1996; Grant et al. 1997). Its specificity toward free histones is not drastically changed within native complexes, but it is now able to modify chromatin substrates with a specificity corresponding to its in vivo action toward H3 and H2B (Grant et al. 1999; Suka et al. 2001). "
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