Zhou Wangbin, Gao Juan, Ma Jing, Cao Lin, Zhang Chi, Zhu Yan, Dong Aiwu, Shen Wen-Hui
Department of Biochemistry, State Key Laboratory of Genetic Engineering, Collaborative Innovation Center for Genetics and Development, International Associated Laboratory of CNRS-Fudan-HUNAU on Plant Epigenome Research, School of Life Sciences, Institute of Plant Biology, Fudan University, Shanghai, 20043, China.
Institut de Biologie Moléculaire des Plantes (IBMP), UPR2357 CNRS, Université de Strasbourg, 12 rue du Général Zimmer, Strasbourg Cédex, 67084, France.
Plant J. 2016 Nov;88(3):397-410. doi: 10.1111/tpj.13256. Epub 2016 Sep 8.
Homologous recombination (HR) of nuclear DNA occurs within the context of a highly complex chromatin structure. Despite extensive studies of HR in diverse organisms, mechanisms regulating HR within the chromatin context remain poorly elucidated. Here we investigate the role and interplay of the histone chaperones NUCLEOSOME ASSEMBLY PROTEIN1 (NAP1) and NAP1-RELATED PROTEIN (NRP) and the ATP-dependent chromatin-remodeling factor INOSITOL AUXOTROPHY80 (INO80) in regulating somatic HR in Arabidopsis thaliana. We show that simultaneous knockout of the four AtNAP1 genes and the two NRP genes in the sextuple mutant m123456-1 barely affects normal plant growth and development. Interestingly, compared with the respective AtNAP1 (m123-1 and m1234-1) or NRP (m56-1) loss-of-function mutants, the sextuple mutant m123456-1 displays an enhanced plant hypersensitivity to UV or bleomycin treatments. Using HR reporter constructs, we show that AtNAP1 and NRP act in parallel to synergistically promote somatic HR. Distinctively, the AtINO80 loss-of-function mutation (atino80-5) is epistatic to m56-1 in plant phenotype and telomere length but hypostatic to m56-1 in HR determinacy. Further analyses show that expression of HR machinery genes and phosphorylation of H2A.X (γ-H2A.X) are not impaired in the mutants. Collectively, our study indicates that NRP and AtNAP1 synergistically promote HR upstream of AtINO80-mediated chromatin remodeling after the formation of γ-H2A.X foci during DNA damage repair.
核DNA的同源重组（HR）发生在高度复杂的染色质结构环境中。尽管对不同生物体中的HR进行了广泛研究，但染色质环境中调节HR的机制仍未得到充分阐明。在这里，我们研究了组蛋白伴侣核小体组装蛋白1（NAP1）和NAP1相关蛋白（NRP）以及ATP依赖性染色质重塑因子肌醇营养缺陷型80（INO80）在调节拟南芥体细胞HR中的作用和相互作用。我们发现，六重突变体m123456-1中四个AtNAP1基因和两个NRP基因的同时敲除几乎不影响正常植物的生长发育。有趣的是，与各自的AtNAP1（m123-1和m1234-1）或NRP（m56-1）功能丧失突变体相比，六重突变体m123456-1对紫外线或博来霉素处理表现出增强的植物超敏反应。使用HR报告构建体，我们表明AtNAP1和NRP平行发挥作用，协同促进体细胞HR。独特的是，AtINO80功能丧失突变（atino80-5）在植物表型和端粒长度方面对m56-1是上位性的，但在HR确定性方面对m56-1是下位性的。进一步分析表明，突变体中HR机制基因的表达和H2A.X（γ-H2A.X）的磷酸化没有受损。总的来说，我们的研究表明，在DNA损伤修复过程中γ-H2A.X焦点形成后，NRP和AtNAP1在AtINO80介导的染色质重塑上游协同促进HR。
