n nnnImpeded DNA replication or a deficiency of its control may criticallythreaten the genetic information of cells, possibly resultingin genome alterations, such as gross chromosomal translocations,microsatellite instabilities, or increased rates of homologousrecombination (HR). We examined an Arabidopsis thaliana linederived from a forward genetic screen, which exhibits an elevatedfrequency of somatic HR. These HR events originate from replicationstress in endoreduplicating cells caused by reduced expressionof the gene coding for the catalytic subunit of the DNA polymerase (POL1). The analysis of recombination types induced by diversealleles of pol1 and by replication inhibitors allows the conclusionthat two not mutually exclusive mechanisms lead to the generationof recombinogenic breaks at replication forks. In plants withweak pol1 alleles, we observe genome instabilities predominantlyat sites with inverted repeats, suggesting the formation andprocessing of aberrant secondary DNA structures as a resultof the accumulation of unreplicated DNA. Stalled and collapsedreplication forks account for the more drastic enhancement ofHR in plants with strong pol1 mutant alleles. Our data suggestthat efficient progression of DNA replication, foremost on thelagging strand, relies on the physiological level of the polymerase complex and that even a minor disturbance of the replicationprocess critically threatens genomic integrity of Arabidopsiscells.展开▼
机译:ABSTRACTn FONT> TH> TR> TABLE> n
n TOP n <字体颜色= 464c53>抽象 FONT> n 介绍 n 结果 n 讨论 n 方法 n 参考文献 n FONT> TH> TR> TABLE> n nnnDNA复制受阻或缺乏控制可能会严重 SU P>威胁细胞的遗传信息,可能导致基因改变中的 SUP>,例如总染色体易位, SUP>微卫星不稳定性或同源 SUP>重组(HR)。我们检查了来自向前遗传筛选的拟南芥 I>品系 SUP>,该品系显示出体细胞HR升高的 SUP>频率。这些HR事件起因于编码DNA聚合酶 SUP> SUP>降低导致的内复制细胞内复制 SUP>压力=“ / math / delta.gif” ALT =“ {delta}” BORDER =“ 0”>( POL 1 I>)。 pol 1 I的不同 SUP>等位基因诱导的重组类型分析>和复制抑制剂的结论是 SUP>,这是两个不互斥的机制导致复制叉处产生重组断裂的 SUP>。在具有 pol 1 I>等位基因的植物中,我们观察到基因组不稳定性主要是在具有反向重复的位点处的 SUP>,这表明由于未复制DNA的积累的结果 SUP>导致异常的二级DNA结构的形成和 SUP>处理。停滞和倒塌的 SUP>复制叉使 pol 1 I>突变等位基因。我们的数据表明 SUP>,DNA复制的有效进展(主要在 SUP>滞后链上)依赖于聚合酶 SUP> 复杂,即使复制 SUP>过程受到很小的干扰也会严重威胁拟南芥(Irabidopsis)的基因组完整性> SUP>单元格。 SUP>
展开▼