Copper homeostasis is crucial for various cellular processes. The balance between nutritional and toxic copper levels is maintained through the regulation of its uptake, distribution, and detoxification via antagonistic actions of two transcription factors, Ace1 and Mac1. Ace1 responds to toxic copper levels by transcriptionally regulating detoxification genes CUP1 and CRS5. Cup1 metallothionein confers protection against toxic copper levels. CUP1 gene regulation is a multifactorial event requiring Ace1, TATA-binding protein (TBP), chromatin remodeler, acetyltransferase (Spt10), and histones. However, the role of histone H3 residues has not been fully elucidated. To investigate the role of the H3 tail in CUP1 transcriptional regulation, we screened the library of histone mutants in copper stress. We identified mutations in H3 (K23Q, K27R, K36Q, Δ5-16, Δ13-16, Δ13-28, Δ25-28, Δ28-31, and Δ29-32) that reduce CUP1 expression. We detected reduced Ace1 occupancy across the CUP1 promoter in K23Q, K36Q, Δ5-16, Δ13-28, Δ25-28, and Δ28-31 mutations correlating with the reduced CUP1 transcription. The majority of these mutations affect TBP occupancy at the CUP1 promoter, augmenting the CUP1 transcription defect. Additionally, some mutants displayed cytosolic protein aggregation upon copper stress. Altogether, our data establish previously unidentified residues of the H3 N-terminal tail and their modifications in CUP1 regulation.

中文翻译：

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组蛋白H3的N末端尾巴调节酿酒酵母中的铜稳态。

铜稳态对于各种细胞过程至关重要。营养铜和有毒铜水平之间的平衡通过两个转录因子Ace1和Mac1的拮抗作用，通过调节其摄取，分布和排毒来保持。Ace1通过转录调节排毒基因CUP1和CRS5对有毒铜水平作出反应。Cup1金属硫蛋白可提供针对有毒铜水平的保护。CUP1基因调控是一个多因素事件，需要Ace1，TATA结合蛋白（TBP），染色质重塑剂，乙酰转移酶（Spt10）和组蛋白。然而，组蛋白H3残基的作用尚未完全阐明。调查H3尾巴在CUP1中的作用转录调控，我们筛选了铜胁迫下组蛋白突变体的文库。我们确定了降低CUP1表达的H3突变（K23Q，K27R，K36Q，Δ5-16，Δ13-16，Δ13-28，Δ25-28，Δ28-31和Δ29-32）。我们检测到与CUP1转录降低相关的K23Q，K36Q，Δ5-16，Δ13-28，Δ25-28和Δ28-31突变中整个CUP1启动子的Ace1占有率降低。这些突变中的大多数会影响CUP1启动子上的TBP占用，从而加剧CUP1转录缺陷。另外，一些突变体在铜胁迫下表现出胞质蛋白聚集。总之，我们的数据确定了H3 N末端尾巴的先前未鉴定残基及其在CUP1调节。