Transcription initiation is a major regulatory step in eukaryotic gene expression. It involves the assembly of general transcription factors and RNA polymerase II into a functional pre-initiation complex at core promoters. The degree of chromatin compaction controls the accessibility of the transcription machinery to template DNA. Co-activators have critical roles in this process by actively regulating chromatin accessibility. Many transcriptional coactivators are multisubunit complexes, organized into distinct structural and functional modules and carrying multiple regulatory activities. The first nuclear histone acetyltransferase (HAT) characterized was General Control Non-derepressible 5 (Gcn5). Gcn5 was subsequently identified as a subunit of the HAT module of the Spt-Ada-Gcn5-acetyltransferase (SAGA) complex, which is an experimental paradigm for multifunctional co-activators. We know today that Gcn5 is the catalytic subunit of multiple distinct co-activator complexes with specific functions. In this review, we summarize recent advances in the structure of Gcn5-containing co-activator complexes, most notably SAGA, and discuss how these new structural insights contribute to better understand their functions. This article is part of a Special Issue entitled: Gcn5: the quintessential histone acetyltransferase.

转录起始是真核基因表达中的主要调控步骤。它涉及在核心启动子处将通用转录因子和RNA聚合酶II组装成功能性预启动复合物。染色质的紧密程度控制着转录机制对模板DNA的可及性。通过积极调节染色质的可及性，共激活剂在这一过程中起着至关重要的作用。许多转录共激活因子是多亚基复合体，组织成不同的结构和功能模块，并具有多种调控活性。第一个核组蛋白乙酰转移酶（HAT）的特征是通用控制不可抑制5（Gcn5）。随后，Gcn5被鉴定为Spt-Ada-Gcn5-乙酰基转移酶（SAGA）复合体HAT模块的亚基，这是多功能共激活剂的实验范式。今天我们知道，Gcn5是具有特定功能的多种不同的共激活复合物的催化亚基。在这篇综述中，我们总结了含Gcn5的共激活物复合物（最著名的是SAGA）在结构上的最新进展，并讨论了这些新的结构见解如何有助于更好地理解其功能。本文是名为“ Gcn5：典型的组蛋白乙酰转移酶”的特刊的一部分。并讨论这些新的结构见解如何有助于更好地理解其功能。本文是名为“ Gcn5：典型的组蛋白乙酰转移酶”的特刊的一部分。并讨论这些新的结构见解如何有助于更好地理解其功能。本文是名为“ Gcn5：典型的组蛋白乙酰转移酶”的特刊的一部分。