Holliday junction resolvases mediate chloroplast nucleoid segregation
Holliday junction resolvases mediate chloroplast nucleoid segregation
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DOI：
10.1126/science.aan0038
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发表时间：
2017-05-12
期刊：
影响因子：
56.9
通讯作者：
Nishimura, Yoshiki
中科院分区：
文献类型：
--
作者：
Kobayashi, Yusuke;Misumi, Osami;Nishimura, Yoshiki
Holliday连接是在同源重组过程中形成的四链DNA结构，通过在原核生物和真核生物中发现的分解酶来解缠，但在植物细胞器中没有发现。在这里，我们通过分析绿藻衣藻突变体叶绿体类核(DNA-蛋白质复合体)分离缺陷，确定单核细胞叶绿体1(MOC1)是叶绿体中的Holliday连接解析酶。MOC1在结构上类似于细菌的Holliday连接解析酶，耐紫外线(Ruv)C，在绿色植物中遗传保守。在拟南芥中，MOC1的表达减少或不表达会导致生长缺陷和叶绿体类核的异常分离。体外生化分析和高速原子力显微镜分析表明，A.thaliana MOC 1(AtMOC1)对称地结合和切割Holliday连接的核心。MOC1可能通过分解Holliday连接来介导绿色体类核的分离。
Holliday junctions, four-stranded DNA structures formed during homologous recombination, are disentangled by resolvases that have been found in prokaryotes and eukaryotes but not in plant organelles. Here, we identify monokaryotic chloroplast 1 (MOC1) as a Holliday junction resolvase in chloroplasts by analyzing a green alga Chlamydomonas reinhardtii mutant defective in chloroplast nucleoid (DNA-protein complex) segregation. MOC1 is structurally similar to a bacterial Holliday junction resolvase, resistance to ultraviolet (Ruv) C, and genetically conserved among green plants. Reduced or no expression of MOC1 in Arabidopsis thaliana leads to growth defects and aberrant chloroplast nucleoid segregation. In vitro biochemical analysis and high-speed atomic force microscopic analysis revealed that A. thaliana MOC 1 (AtMOC1) binds and cleaves the core of Holliday junctions symmetrically. MOC1 may mediate chloroplast nucleoid segregation in green plants by resolving Holliday junctions.