Differential effect of histone H3.3 depletion on retroviral repression in embryonic stem cells.

IF 5.7 2区 医学 Q1 Medicine
Ayellet Tal, Jose David Aguilera, Igor Bren, Carmit Strauss, Sharon Schlesinger
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Abstract

Background: Integration of retroviruses into the host genome can impair the genomic and epigenomic integrity of the cell. As a defense mechanism, epigenetic modifications on the proviral DNA repress retroviral sequences in mouse embryonic stem cells (ESC). Here, we focus on the histone 3 variant H3.3, which is abundant in active transcription zones, as well as centromeres and heterochromatinized repeat elements, e.g., endogenous retroviruses (ERV).

Results: To understand the involvement of H3.3 in the epigenetic silencing of retroviral sequences in ESC, we depleted the H3.3 genes in ESC and transduced the cells with GFP-labeled MLV pseudovirus. This led to altered retroviral repression and reduced Trim28 recruitment, which consequently led to a loss of heterochromatinization in proviral sequences. Interestingly, we show that H3.3 depletion has a differential effect depending on which of the two genes coding for H3.3, H3f3a or H3f3b, are knocked out. Depletion of H3f3a resulted in a transient upregulation of incoming retroviral expression and ERVs, while the depletion of H3f3b did not have the same effect and repression was maintained. However, the depletion of both genes resulted in a stable activation of the retroviral promoter. These findings suggest that H3.3 is important for regulating retroviral gene expression in mouse ESC and provide evidence for a distinct function of the two H3.3 genes in this regulation. Furthermore, we show that Trim28 is needed for depositing H3.3 in retroviral sequences, suggesting a functional interaction between Trim28 recruitment and H3.3 loading.

Conclusions: Identifying the molecular mechanisms by which H3.3 and Trim28 interact and regulate retroviral gene expression could provide a deeper understanding of the fundamental processes involved in retroviral silencing and the general regulation of gene expression, thus providing new answers to a central question of stem cell biology.

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组蛋白H3.3缺失对胚胎干细胞逆转录病毒抑制的差异效应。
背景:逆转录病毒整合到宿主基因组中会损害细胞基因组和表观基因组的完整性。作为一种防御机制,前病毒DNA的表观遗传修饰抑制小鼠胚胎干细胞(ESC)中的逆转录病毒序列。在这里,我们关注的是组蛋白3变体H3.3,它在活性转录区、着丝粒和异染色质重复元件(如内源性逆转录病毒(ERV))中丰富。结果:为了了解H3.3在ESC逆转录病毒序列的表观遗传沉默中的作用,我们在ESC中去除H3.3基因,并用gfp标记的MLV假病毒转导细胞。这导致逆转录病毒抑制的改变和Trim28募集的减少,从而导致原病毒序列中异染色化的缺失。有趣的是,我们发现H3.3缺失会产生不同的影响,这取决于编码H3.3的两个基因(H3f3a或H3f3b)中哪一个被敲除。H3f3a的缺失导致传入的逆转录病毒表达和erv的短暂上调,而H3f3b的缺失没有同样的效果,并且抑制得以维持。然而,这两个基因的缺失导致了逆转录病毒启动子的稳定激活。这些发现表明H3.3对于调节小鼠ESC中逆转录病毒基因的表达是重要的,并提供了两个H3.3基因在这种调节中的不同功能的证据。此外,我们发现Trim28是在逆转录病毒序列中沉积H3.3所必需的,这表明Trim28的募集和H3.3装载之间存在功能上的相互作用。结论:确定H3.3和Trim28相互作用和调控逆转录病毒基因表达的分子机制,可以更深入地了解逆转录病毒沉默和基因表达的一般调控的基本过程,从而为干细胞生物学的核心问题提供新的答案。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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来源期刊
Clinical Epigenetics
Clinical Epigenetics Biochemistry, Genetics and Molecular Biology-Developmental Biology
CiteScore
8.90
自引率
5.30%
发文量
150
审稿时长
12 weeks
期刊介绍: Clinical Epigenetics, the official journal of the Clinical Epigenetics Society, is an open access, peer-reviewed journal that encompasses all aspects of epigenetic principles and mechanisms in relation to human disease, diagnosis and therapy. Clinical trials and research in disease model organisms are particularly welcome.
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