A specific role for importin-5 and NASP in the import and nuclear hand-off of monomeric H3.
A specific role for importin-5 and NASP in the import and nuclear hand-off of monomeric H3.
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DOI：
10.7554/elife.81755
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发表时间：
2022-09-06
期刊：
影响因子：
7.7
通讯作者：
Bowman AJ
中科院分区：
文献类型：
--
作者：
Pardal AJ;Bowman AJ
核心组蛋白包装染色体DNA并调节基因组交易，其核输入和沉积涉及输入β蛋白和专用的组蛋白伴侣。此前，一组蛋白H3-H4二聚体被分离到与进口蛋白4 （Imp4）和伴侣蛋白ASF1结合，表明H3和H4在细胞核进口前在细胞质中折叠在一起。然而，其他研究表明单核H3在细胞核中存在，表明存在输入后折叠途径。在这里，我们报道了与细胞质H3相关的主要进口蛋白是进口蛋白-5 (Imp5)，它将其单体货物交给核sNASP。与Imp4不同的是，Imp5与含有组成单体突变的H3和H4结合，并与细胞质中新合成的单体H3结合。组成单体H3保留了与NASP的相互作用，而单体H4保留了与HAT1和RBBP7的特异性相互作用。NASP相互作用物的高分辨率分离显示“s”异构体而不是“t”异构体与单体H3结合，而这两种异构体都与H3- h4二聚体在至少三个离散的多伴侣配合物中结合。体外结合实验显示sNASP和Imp5在结合H3时具有互他性，这表明与组蛋白转移所需的gtp结合形式的Ran直接竞争相互作用位点。最后，使用脉冲追踪分析，我们发现细胞质系住的组蛋白在到达细胞核之前不会与内源性NASP相互作用，然后它们迅速结合。我们提出了单个H3传递给细胞核内sNASP的Imp5特异性导入途径，以及涉及Imp5和HAT1-RBBP7复合物的平行H4途径，随后是核折叠和传递给沉积因子。
Core histones package chromosomal DNA and regulate genomic transactions, with their nuclear import and deposition involving importin-β proteins and a dedicated repertoire of histone chaperones. Previously, a histone H3-H4 dimer has been isolated bound to importin-4 (Imp4) and the chaperone ASF1, suggesting that H3 and H4 fold together in the cytoplasm before nuclear import. However, other studies have shown the existence of monomeric H3 in the nucleus, indicating a post-import folding pathway. Here, we report that the predominant importin associated with cytoplasmic H3 is importin-5 (Imp5), which hands off its monomeric cargo to nuclear sNASP. Imp5, in contrast to Imp4, binds to both H3 and H4 containing constitutively monomeric mutations and binds to newly synthesised, monomeric H3 tethered in the cytoplasm. Constitutively monomeric H3 retains its interaction with NASP, whereas monomeric H4 retains interactions specifically with HAT1 and RBBP7. High-resolution separation of NASP interactors shows the ‘s’ isoform but not the ‘t’ isoform associates with monomeric H3, whilst both isoforms associate with H3-H4 dimers in at least three discrete multi-chaperoning complexes. In vitro binding experiments show mutual exclusivity between sNASP and Imp5 in binding H3, suggesting direct competition for interaction sites, with the GTP-bound form of Ran required for histone transfer. Finally, using pulse-chase analysis, we show that cytoplasm-tethered histones do not interact with endogenous NASP until they reach the nucleus, whereupon they bind rapidly. We propose an Imp5-specific import pathway for monomeric H3 that hands off to sNASP in the nucleus, with a parallel H4 pathway involving Imp5 and the HAT1-RBBP7 complex, followed by nuclear folding and hand-off to deposition factors.
核分离过程中的蛋白质损失。
影响因子：
7.8
作者：
Paine, P L;Austerberry, C F;Desjarlais, L J;Horowitz, S B
通讯作者：
Horowitz, S B
Hat2p 识别组蛋白 H3 尾部，以指定 Hat1p/Hat2p 复合物对新合成的 H3/H4 异二聚体进行乙酰化
影响因子：
10.5
作者：
Li Y;Zhang L;Liu T;Chai C;Fang Q;Wu H;Agudelo Garcia PA;Han Z;Zong S;Yu Y;Zhang X;Parthun MR;Chai J;Xu RM;Yang M
通讯作者：
Yang M