组蛋白伴侣介导核小体的组装和拆卸，并参与基本上所有依赖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功能异常可导致染色质紧实度改变，重复性元素系统性丢失或DNA损伤增加，从而清楚地表明了其严重性。 在没有功能性CAF-1的情况下如何保持染色质组成仍然遥遥无期。
本研究表明，破坏H2A-H2B组蛋白伴侣分子核糖体组装蛋白1（NAP1）可抑制FAS1功能丧失表型。 四倍体突变体fas1 nap1; 1 nap1; 2 nap1; 3显示野生型生长，对遗传毒性胁迫的敏感性降低以及端粒和45S rDNA丢失的抑制。 fas1 nap1; 1 nap1; 2 nap1; 3植物的染色质较微球菌核酸酶更难获得，并且与fas1相比，核H3.1和H3.3组蛋白池发生变化。 一致地，NAP1和H3之间的缔合发生在原生质体内的细胞质和细胞核中。
总而言之，我们表明NAP1蛋白在fas1的DNA修复中起着至关重要的作用，而fas1通过调节细胞核中H3的水平与核小体装配耦合。
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.
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