Duc Céline, Benoit Matthias, Le Goff Samuel, Simon Lauriane, Poulet Axel, Cotterell Sylviane, Tatout Christophe, Probst Aline V
Génétique, Reproduction et Développement, CNRS UMR 6293, Clermont Université, INSERM U1103, 24 Avenue des Landais, BP 80026, Aubière Cedex, 63171, France.
Plant J. 2015 Mar;81(5):707-22. doi: 10.1111/tpj.12758.
Chromatin organization is essential for coordinated gene expression, genome stability, and inheritance of epigenetic information. The main components involved in chromatin assembly are specific complexes such as Chromatin Assembly Factor 1 (CAF-1) and Histone Regulator (HIR), which deposit histones in a DNA synthesis-dependent or -independent manner, respectively. Here, we characterize the role of the plant orthologs Histone Regulator A (HIRA), Ubinuclein (UBN) and Calcineurin Binding protein 1 (CABIN1), which constitute the HIR complex. Arabidopsis loss-of-function mutants for the various subunits of the complex are viable, but hira mutants show reduced fertility. We show that loss of HIRA reduces extractable histone H3 protein levels and decreases nucleosome occupancy at both actively transcribed genes and heterochromatic regions. Concomitantly, HIRA contributes to maintenance of silencing of pericentromeric repeats and certain transposons. A genetic analysis based on crosses between mutants deficient in subunits of the CAF-1 and HIR complexes showed that simultaneous loss of both the CAF-1 and HIR histone H3 chaperone complexes severely affects plant survival, growth and reproductive development. Our results suggest that HIRA partially rescues impaired histone deposition in fas mutants to preserve nucleosome occupancy, implying plasticity in histone variant interaction and deposition.
染色质组织对于协调基因表达、基因组稳定性以及表观遗传信息的遗传至关重要。参与染色质组装的主要成分是特定的复合物，如染色质组装因子1（CAF-1）和组蛋白调节因子（HIR），它们分别以依赖或不依赖DNA合成的方式沉积组蛋白。在这里，我们描述了构成HIR复合物的植物直系同源物组蛋白调节因子A（HIRA）、泛核蛋白（UBN）和钙调神经磷酸酶结合蛋白1（CABIN1）的作用。该复合物各个亚基的拟南芥功能缺失突变体是可存活的，但hira突变体的育性降低。我们发现，HIRA的缺失会降低可提取的组蛋白H3蛋白水平，并减少活跃转录基因和异染色质区域的核小体占有率。同时，HIRA有助于维持着丝粒周围重复序列和某些转座子的沉默。基于CAF-1和HIR复合物亚基缺陷突变体之间杂交的遗传分析表明，CAF-1和HIR组蛋白H3伴侣复合物的同时缺失会严重影响植物的存活、生长和生殖发育。我们的结果表明，HIRA部分挽救了fas突变体中受损的组蛋白沉积以维持核小体占有率，这意味着组蛋白变体相互作用和沉积具有可塑性。
