Yeast Gcn5 functions in two multisubunit complexes to acetylate nucleosomal histones: Characterization of an Ada complex and the SAGA (Spt/Ada) complex
Yeast Gcn5 functions in two multisubunit complexes to acetylate nucleosomal histones: Characterization of an Ada complex and the SAGA (Spt/Ada) complex
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DOI：
10.1101/gad.11.13.1640
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发表时间：
1997-07-01
影响因子：
10.5
通讯作者：
Workman, JL
中科院分区：
文献类型：
--
作者：
Grant, PA;Duggan, L;Workman, JL
转录衔接蛋白Gcn5已被鉴定为核组蛋白乙酰转移酶（HAT）。虽然重组酵母Gcn5能有效地使游离组蛋白乙酰化，但它不能使核小体中含有的组蛋白乙酰化，这表明染色体组蛋白的乙酰化需要额外的成分。我们在这里报道了Gcn5作为催化亚基在两个高分子质量的天然HAT复合物中起作用，它们的表观分子质量分别为0.8和1.8兆道尔顿（MD），可使核小体组蛋白乙酰化。含有0.8和1.8 md的gcn5复合物都与Adn2缩合，并在gcn5 Delta、ada2 Delta或ada3 Delta酵母菌株中丢失，说明这些HAT复合物是真正的天然ada转录接头复合物。重要的是，1.8-MD接头/HAT复合体还含有与tata结合蛋白（TBP）功能相关的Spt基因产物。该复合物在spt20/ada5 δ和spt7 δ菌株中缺失，而Spt3、spt7、spt20/ada5、Ada2和Gcn5均与该核小体HAT复合物共化。因此，1.8-MD接头/HAT复合体说明了Ada和Spt基因产物之间的相互作用，并证实了遗传和生化研究证明的含有Spt蛋白TBP组的复合体的存在。我们将这种新的转录调控复合体命名为SAGA （Spt-Ada-Gcn5-Acetyltransferase）。Gcn5作为Ada和SAGA接子复合物中的组蛋白乙酰转移酶的功能表明，在转录激活过程中，组蛋白乙酰化在与转录激活因子和一般转录因子（即TBP）相互作用介导的转录激活步骤中具有重要作用。
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 Adn2 and are lost in gcn5 Delta, ada2 Delta, or ada3 Delta 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/ada5 Delta and spt7 Delta 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).