Background

Posttranslational histone modifications play a critical role in the regulation of gene transcription underlying synaptic plasticity and memory formation. One such epigenetic change is histone ubiquitination, a process that is mediated by the ubiquitin–proteasome system in a manner similar to that by which proteins are normally targeted for degradation. However, histone ubiquitination mechanisms are poorly understood in the brain and in learning. In this article, we describe a new role for the ubiquitin–proteasome system in histone crosstalk, showing that learning-induced monoubiquitination of histone H2B (H2Bubi) is required for increases in the transcriptionally active H3 lysine 4 trimethylation (H3K4me3) mark at learning-related genes in the hippocampus.

Methods

Using a series of molecular, biochemical, electrophysiological, and behavioral experiments, we interrogated the effects of short interfering RNA–mediated knockdown and CRISPR (clustered regularly interspaced short palindromic repeats)-mediated upregulation of ubiquitin ligases, deubiquitinating enzymes and histone methyltransferases in the rat dorsal hippocampus during memory consolidation.

Results

We show that H2Bubi recruits H3K4me3 through a process that is dependent on the 19S proteasome subunit RPT6 and that a loss of H2Bubi in the hippocampus prevents learning-induced increases in H3K4me3, gene transcription, synaptic plasticity, and memory formation. Furthermore, we show that CRISPR–dCas9-mediated increases in H2Bubi promote H3K4me3 and memory formation under weak training conditions and that promoting histone methylation does not rescue memory impairments resulting from loss of H2Bubi.

Conclusions

These results suggest that H2B ubiquitination regulates histone crosstalk in learning by way of nonproteolytic proteasome function, demonstrating a novel mechanism by which histone modifications are coordinated in response to learning.

中文翻译：

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蛋白酶体亚基 RPT6 对组蛋白 H2B 的泛素化控制记忆形成过程中的组蛋白甲基化染色质动态

 背景

翻译后组蛋白修饰在突触可塑性和记忆形成的基因转录调节中发挥着关键作用。其中一个表观遗传变化是组蛋白泛素化，这是一种由泛素-蛋白酶体系统介导的过程，其方式类似于蛋白质通常被靶向降解的方式。然而，人们对大脑和学习中的组蛋白泛素化机制知之甚少。在本文中，我们描述了泛素-蛋白酶体系统在组蛋白串扰中的新作用，表明学习诱导的组蛋白 H2B (H2Bubi) 单泛素化是学习时转录活性 H3 赖氨酸 4 三甲基化 (H3K4me3) 标记增加所必需的。海马体中的相关基因。

 方法

通过一系列分子、生物化学、电生理学和行为实验，我们探讨了短干扰 RNA 介导的敲低和 CRISPR（成簇规则间隔短回文重复序列）介导的大鼠中泛素连接酶、去泛素化酶和组蛋白甲基转移酶的上调效果。记忆巩固期间的背海马体。

 结果

我们发现，H2Bubi 通过依赖 19S 蛋白酶体亚基 RPT6 的过程招募 H3K4me3，并且海马中 H2Bubi 的缺失会阻止学习诱导的 H3K4me3、基因转录、突触可塑性和记忆形成的增加。此外，我们发现，在弱训练条件下，CRISPR-dCas9 介导的 H2Bubi 增加可促进 H3K4me3 和记忆形成，并且促进组蛋白甲基化并不能挽救因 H2Bubi 丢失而导致的记忆损伤。

 结论

这些结果表明，H2B 泛素化通过非蛋白水解蛋白酶体功能调节学习中的组蛋白串扰，证明了一种协调组蛋白修饰响应学习的新机制。