Histone chaperones mediate the assembly and disassembly of nucleosomes and participate in essentially all DNA‐dependent cellular processes. In Arabidopsis thaliana, loss‐of‐function of FAS1 or FAS2 subunits of the H3‐H4 histone chaperone complex CHROMATIN ASSEMBLY FACTOR 1 (CAF‐1) has a dramatic effect on plant morphology, growth and overall fitness. CAF‐1 dysfunction can lead to altered chromatin compaction, systematic loss of repetitive elements or increased DNA damage, clearly demonstrating its severity. How chromatin composition is maintained without functional CAF‐1 remains elusive. Here we show that disruption of the H2A‐H2B histone chaperone NUCLEOSOME ASSEMBLY PROTEIN 1 (NAP1) suppresses the FAS1 loss‐of‐function phenotype. The quadruple mutant fas1 nap1;1 nap1;2 nap1;3 shows wild‐type growth, decreased sensitivity to genotoxic stress and suppression of telomere and 45S rDNA loss. Chromatin of fas1 nap1;1 nap1;2 nap1;3 plants is less accessible to micrococcal nuclease and the nuclear H3.1 and H3.3 histone pools change compared to fas1. Consistently, association between NAP1 and H3 occurs in the cytoplasm and nucleus in vivo in protoplasts. Altogether we show that NAP1 proteins play an essential role in DNA repair in fas1, which is coupled to nucleosome assembly through modulation of H3 levels in the nucleus.

中文翻译：

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拟南芥中 NAP1 基因的破坏抑制了 fas1 突变表型，增强了基因组稳定性并改变了染色质压实

组蛋白伴侣介导核小体的组装和分解，并基本上参与所有依赖于 DNA 的细胞过程。在拟南芥中，H3-H4 组蛋白伴侣复合物染色质组装因子 1 (CAF-1) 的 FAS1 或 FAS2 亚基的功能丧失对植物形态、生长和整体适应性具有显着影响。CAF-1 功能障碍可导致染色质压实改变、重复元件的系统性丢失或 DNA 损伤增加，清楚地表明其严重性。在没有功能性 CAF-1 的情况下如何维持染色质组成仍然难以捉摸。在这里，我们表明 H2A-H2B 组蛋白伴侣核小体组装蛋白 1 (NAP1) 的破坏抑制了FAS1功能丧失表型。四重突变体fas1 nap1;1 nap1;2 nap1;3显示出野生型生长、对基因毒性应激的敏感性降低以及端粒和 45S rDNA 丢失的抑制。的染色质FAS1 NAP1; 1个NAP1; 2 NAP1; 3种植物是微球菌核酸酶和核H3.1和组蛋白H3.3池不易进入的改变相比FAS1。一致地，NAP1 和 H3 之间的关联发生在体内原生质体的细胞质和细胞核中。总之，我们表明 NAP1 蛋白在fas1中的 DNA 修复中起重要作用，fas1通过调节细胞核中的 H3 水平与核小体组装相结合。