Arabidopsis thaliana RNase H2 Deficiency Counteracts the Needs for the WEE1 Checkpoint Kinase but Triggers Genome Instability
Arabidopsis thaliana RNase H2 Deficiency Counteracts the Needs for the WEE1 Checkpoint Kinase but Triggers Genome Instability
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DOI：
10.1105/tpc.114.128108
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发表时间：
2014-09-01
期刊：
影响因子：
11.6
通讯作者：
De Veylder, Lieven
中科院分区：
文献类型：
--
作者：
Kalhorzadeh, Pooneh;Hu, Zhubing;De Veylder, Lieven
WEE 1激酶是拟南芥复制缺陷中一个重要的细胞周期检查点调节因子。而在非胁迫条件下，WEE 1缺陷植物正常发育，它们不能适应复制抑制条件，导致DNA损伤的积累和细胞分裂能力的丧失。我们确定了编码核糖核酸酶H2（RNase H2）复合物亚基的基因的突变等位基因，该复合物以其在从DNA-RNA双链体中去除核糖核苷酸中的作用而闻名，作为WEE 1敲除植物的抑制突变体。RNase H2缺陷引发了同源重组（HR）的增加，与γ-H2 AX灶的积累相关。然而，由于HR在复制胁迫下对WEE 1缺陷型植物的生长产生负面影响，因此它不能解释WEE 1敲除植物的复制缺陷的拯救。相反，观察到的核糖核苷酸掺入DNA中的增加表明，用核糖核苷酸取代脱氧核苷酸消除了复制应激下对WEE 1的需要。引人注目的是，DNA中核糖核苷酸掺入的增加与小碱基对缺失的发生相关，确定RNase H2复合物是基因组不稳定性的重要抑制因子。
The WEE1 kinase is an essential cell cycle checkpoint regulator in Arabidopsis thaliana plants experiencing replication defects. Whereas under non-stress conditions WEE1-deficient plants develop normally, they fail to adapt to replication inhibitory conditions, resulting in the accumulation of DNA damage and loss of cell division competence. We identified mutant alleles of the genes encoding subunits of the ribonuclease H2 (RNase H2) complex, known for its role in removing ribonucleotides from DNA-RNA duplexes, as suppressor mutants of WEE1 knockout plants. RNase H2 deficiency triggered an increase in homologous recombination (HR), correlated with the accumulation of gamma-H2AX foci. However, as HR negatively impacts the growth of WEE1-deficient plants under replication stress, it cannot account for the rescue of the replication defects of the WEE1 knockout plants. Rather, the observed increase in ribonucleotide incorporation in DNA indicates that the substitution of deoxynucleotide with ribonucleotide abolishes the need for WEE1 under replication stress. Strikingly, increased ribonucleotide incorporation in DNA correlated with the occurrence of small base pair deletions, identifying the RNase H2 complex as an important suppressor of genome instability.