Histone H2A Variants Enhance the Initiation of Base Excision Repair in Nucleosomes
Histone H2A Variants Enhance the Initiation of Base Excision Repair in Nucleosomes
复制标题
DOI：
10.1021/acschembio.9b00229
复制
发表时间：
2019-05-01
影响因子：
4
通讯作者：
Delaney, Sarah
中科院分区：
文献类型：
--
作者：
Li, Chuxuan;Delaney, Sarah
用组蛋白变异体取代经典的组蛋白变异体可以深刻改变染色质的结构，从而影响多种生物过程。在这里，我们研究了来自H_2A家族的组蛋白变体对碱基切除修复(BER)酶尿嘧啶DNA糖基酶(UDG)和单链选择性单功能尿嘧啶DNA糖基酶(UDG)切割尿嘧啶(U)的影响。使用全球分布的U：G碱基对的DNA群体，在H_2A.Z和含有大H_2A的核小体核心颗粒(NCP)中观察到增强的切除。溶液可及性降低的U在标准NCP中表现出有限的UDG活性，但在变种NCP中更容易切除，反映了这些变异体在原本修复较差的部位促进切除的能力。我们还发现，在变异型NCP中，剪裁水平增加最大的U聚集在变异体和典型的H2A之间具有不同结构特征的区域。在大分子H_2A NCP的DNA末端的35-40个碱基内，两种糖基酶的活性都与游离双链体上的活性相当。我们表明，这种高水平的活性来自大分子H_2A NCP系综中的两个不同物种：八体体和六体体。这些观察揭示了H2A变体在促进BER和防止染色质背景下的突变方面的潜在功能。
Substituting histone variants for their canonical counterparts can profoundly alter chromatin structure, thereby impacting multiple biological processes. Here, we investigate the influence of histone variants from the H2A family on the excision of uracil (U) by the base excision repair (BER) enzymes uracil DNA glycosylase (UDG) and single strand selective monofunctional uracil DNA glycosylase. Using a DNA population with globally distributed U:G base pairs, enhanced excision is observed in H2A.Z and macroH2A-containing nucleosome core particles (NCPs). The U with reduced solution accessibility exhibit limited UDG activity in canonical NCPs but are more readily excised in variant NCPs, reflecting the ability of these variants to facilitate excision at sites that are otherwise poorly repaired. We also find that U with the largest increase in the level of excision in variant NCPs are clustered in regions with differential structural features between the variants and canonical H2A. Within 35-40 bp of the DNA terminus in macroH2A NCPs, the activities of both glycosylases are comparable to that on the free duplex. We show that this high level of activity results from two distinct species within the macroH2A NCP ensemble: octasomes and hexasomes. These observations reveal potential functions for H2A variants in promoting BER and preventing mutagenesis within the context of chromatin.