Centre de Recherche, Hôpital Maisonneuve-Rosemont, Université de Montréal, Montréal, QC H1T 2M4, Canada.
DNA Repair (Amst). 2010 Jun 4;9(6):690-9. doi: 10.1016/j.dnarep.2010.03.006. Epub 2010 Apr 15.
Mutations in Aprataxin cause the neurodegenerative syndrome ataxia oculomotor apraxia type 1. Aprataxin catalyzes removal of adenosine monophosphate (AMP) from the 5' end of a DNA strand, which results from an aborted attempt to ligate a strand break containing a damaged end. To gain insight into which DNA lesions are substrates for Aprataxin action in vivo, we deleted the Saccharomyces cerevisiae HNT3 gene, which encodes the Aprataxin homolog, in combination with known DNA repair genes. While hnt3Delta single mutants were not sensitive to DNA damaging agents, loss of HNT3 caused synergistic sensitivity to H(2)O(2) in backgrounds that accumulate strand breaks with blocked termini, including apn1Delta apn2Delta tpp1Delta and ntg1Delta ntg2Delta ogg1Delta. Loss of HNT3 in rad27Delta cells, which are deficient in long-patch base excision repair (LP-BER), resulted in synergistic sensitivity to H(2)O(2) and MMS, indicating that Hnt3 and LP-BER provide parallel pathways for processing 5' AMPs. Loss of HNT3 also increased the sister chromatid exchange frequency. Surprisingly, HNT3 deletion partially rescued H(2)O(2) sensitivity in recombination-deficient rad51Delta and rad52Delta cells, suggesting that Hnt3 promotes formation of a repair intermediate that is resolved by recombination.
Aprataxin 基因突变导致神经退行性疾病眼动性共济失调伴运动不能 1 型。Aprataxin 催化从 DNA 链 5'端去除单磷酸腺苷（AMP），这是由于连接包含受损末端的链断裂的尝试失败而导致的。为了深入了解 Aprataxin 在体内作用的 DNA 损伤类型，我们删除了编码 Aprataxin 同源物的酿酒酵母 HNT3 基因，同时结合已知的 DNA 修复基因。虽然 hnt3Delta 单突变体对 DNA 损伤剂不敏感，但在积累具有阻塞末端的链断裂的背景下，包括 apn1Delta apn2Delta tpp1Delta 和 ntg1Delta ntg2Delta ogg1Delta，HNT3 的缺失导致与 H2O2 的协同敏感性。在 rad27Delta 细胞（长补丁碱基切除修复（LP-BER）有缺陷）中缺失 HNT3 导致与 H2O2 和 MMS 的协同敏感性，表明 Hnt3 和 LP-BER 为处理 5' AMPs 提供了并行途径。HNT3 的缺失也增加了姐妹染色单体交换频率。令人惊讶的是，HNT3 缺失部分挽救了重组缺陷的 rad51Delta 和 rad52Delta 细胞对 H2O2 的敏感性，表明 Hnt3 促进了由重组解决的修复中间体的形成。
