The nuclear sulfenome of Arabidopsis: spotlight on histone acetyltransferase GCN5 regulation through functional thiols

In aerobic life forms, reactive oxygen species (ROS) are produced by the partial reduction of oxygen during energy-generating metabolic processes. In plants, ROS production increases during periods of both abiotic and biotic stress, severely overloading the antioxidant systems. Hydrogen peroxide (H2O2) plays a central role in cellular redox homeostasis and signaling by oxidising crucial cysteines to sulfenic acid, which is considered a biologically relevant post-translational modification (PTM). Until now, the impact of the nucleus on cellular redox homeostasis has been relatively unexplored. The regulation of histone-modifying enzymes by oxidative PTMs at redox-sensitive cysteine or tyrosine residues is particularly intriguing because it allows the integration of redox signaling mechanisms with chromatin control of transcriptional activity. One of the most extensively studied histone acetyltransferases is the conserved GENERAL CONTROL NONDEPRESSIBLE 5 (GCN5) complex. This study investigated the nuclear sulfenome in Arabidopsis thaliana by expressing a nuclear variant of the Yeast Activation Protein-1 (YAP1) probe and identified 225 potential redox-active proteins undergoing S-sulfenylation. Mass spectrometry analysis further confirmed the S-sulfenylation of GCN5 at cysteines 293, 368, and 400, and their functional significance and impact on the GCN5 protein-protein interaction network were assessed using cysteine-to-serine mutagenesis.

在需氧生物中，活性氧簇（reactive oxygen species, ROS）由产能量代谢过程中氧的不完全还原所产生。在植物中，活性氧簇的产生在非生物与生物胁迫时期均会增加，进而严重超出抗氧化系统的负荷能力。过氧化氢（Hydrogen peroxide, H₂O₂）通过将关键半胱氨酸氧化为次磺酸，在细胞氧化还原稳态与信号通路中发挥核心作用，这一过程被认为是一种具有生物学相关性的翻译后修饰（post-translational modification, PTM）。迄今为止，细胞核对细胞氧化还原稳态的影响仍相对未被深入探究。氧化型翻译后修饰在氧化还原敏感的半胱氨酸或酪氨酸残基上对组蛋白修饰酶的调控尤其引人关注，因为这一机制可将氧化还原信号通路与染色质调控的转录活性相整合。目前研究最为广泛的组蛋白乙酰转移酶之一是保守的通用调控非阻遏5（GENERAL CONTROL NONDEPRESSIBLE 5, GCN5）复合物。本研究通过表达酵母激活蛋白1（Yeast Activation Protein-1, YAP1）探针的核定位变体，对拟南芥（Arabidopsis thaliana）的核亚磺酰化组进行了研究，并鉴定出225种可能发生S-亚磺酰化的氧化还原活性蛋白。质谱分析进一步证实了GCN5在半胱氨酸293、368与400位点发生了S-亚磺酰化，并通过半胱氨酸突变为丝氨酸的诱变技术评估了这些位点的功能意义及其对GCN5蛋白质相互作用网络的影响。