Department of Biochemistry and Biophysics, University of California, San Francisco, CA, 94158, USA.
Proc Natl Acad Sci U S A. 2011 Jun 28;108(26):10620-5. doi: 10.1073/pnas.1019735108. Epub 2011 Jun 14.
Recent work has identified several posttranslational modifications (PTMs) on chromatin-remodeling complexes. Compared with our understanding of histone PTMs, significantly less is known about the functions of PTMs on remodeling complexes, because identification of their specific roles often is hindered by the presence of redundant pathways. Remodels the Structure of Chromatin (RSC) is an essential, multifunctional ATP-dependent chromatin-remodeling enzyme of Saccharomyces cerevisiae that preferentially binds acetylated nucleosomes. RSC is itself acetylated by Gcn5 on lysine 25 (K25) of its Rsc4 subunit, adjacent to two tandem bromodomains. It has been shown that an intramolecular interaction between the acetylation mark and the proximal bromodomain inhibits binding of the second bromodomain to acetylated histone H3 tails. We report here that acetylation does not significantly alter the catalytic activity of RSC or its ability to recognize histone H3-acetylated nucleosomes preferentially in vitro. However, we find that Rsc4 acetylation is crucial for resistance to DNA damage in vivo. Epistatic miniarray profiling of the rsc4-K25R mutant reveals an interaction with mutants in the INO80 complex, a mediator of DNA damage and replication stress tolerance. In the absence of a core INO80 subunit, rsc4-K25R mutants display sensitivity to hydroxyurea and delayed S-phase progression under DNA damage. Thus, Rsc4 helps promote resistance to replication stress, and its single acetylation mark regulates this function. These studies offer an example of acetylation of a chromatin-remodeling enzyme controlling a biological output of the system rather than regulating its core enzymatic properties.
最近的研究已经确定了几个染色质重塑复合物上的翻译后修饰（PTMs）。与我们对组蛋白 PTMs 的理解相比，关于重塑复合物上 PTMs 的功能知之甚少，因为它们特定作用的识别通常会受到冗余途径的存在的阻碍。重塑染色质结构（RSC）是酿酒酵母中必需的、多功能的 ATP 依赖性染色质重塑酶，它优先结合乙酰化核小体。RSC 本身被 Gcn5 在其 Rsc4 亚基的赖氨酸 25（K25）上乙酰化，靠近两个串联溴结构域。已经表明，乙酰化标记与近端溴结构域之间的分子内相互作用抑制了第二个溴结构域与乙酰化组蛋白 H3 尾巴的结合。我们在这里报告说，乙酰化不会显著改变 RSC 的催化活性或其体外优先识别组蛋白 H3 乙酰化核小体的能力。然而，我们发现 Rsc4 乙酰化对于体内抵抗 DNA 损伤至关重要。rsc4-K25R 突变体的表型微阵列分析揭示了与 INO80 复合物突变体的相互作用，INO80 复合物是 DNA 损伤和复制应激耐受的介质。在缺乏核心 INO80 亚基的情况下，rsc4-K25R 突变体对羟基脲敏感，并且在 DNA 损伤下 S 期进展延迟。因此，Rsc4 有助于促进对复制应激的抗性，其单一乙酰化标记调节此功能。这些研究提供了一个例子，即染色质重塑酶的乙酰化控制着系统的生物学输出，而不是调节其核心酶学特性。
