CAG Expansions Are Genetically Stable and Form Nontoxic Aggregates in Cells Lacking Endogenous Polyglutamine Proteins.
CAG Expansions Are Genetically Stable and Form Nontoxic Aggregates in Cells Lacking Endogenous Polyglutamine Proteins.
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CAG 扩增具有遗传稳定性，并在缺乏内源性聚谷氨酰胺蛋白的细胞中形成无毒聚集体。
DOI：
10.1128/mbio.01367-16
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发表时间：
2016
期刊：
影响因子：
6.4
通讯作者：
Supattapone,Surachai
中科院分区：
文献类型：
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作者：
Zurawel,AshleyA;Kabeche,Ruth;DiGregorio,SonjaE;Deng,Lin;Menon,KartikeyaM;Opalko,Hannah;Duennwald,MartinL;Moseley,JamesB;Supattapone,Surachai
含有多聚谷氨酰胺(PolyQ)区域的蛋白质在几乎所有真核生物中都存在，尽管频率不同。在人类中，亨廷顿蛋白(Htt)等具有异常扩大的多Q区域的蛋白质会导致神经退行性疾病，如亨廷顿病(HD)。为了研究内源性多Q聚集如何调节多Q聚集和毒性，我们在裂殖酵母中表达了多Q扩展Htt片段(PolyQ Htt)。与其他单细胞真菌(如酿酒酵母)形成鲜明对比的是，S.pombe唯一缺乏超过10个Q重复的蛋白质。我们发现，PolyQ Htt仅在S.pombe细胞内形成聚集体，具有超长的PolyQ扩展。令人惊讶的是，尽管胞浆和胞核中都存在多聚Q Htt聚集体，但在S.pombe细胞中没有观察到明显的生长缺陷。此外，聚合酶链式反应分析表明，在转化和多次分裂后，多聚Q编码的DNA重复区域保持不变，而在其他生物中，多聚Q DNA序列的遗传不稳定。这些结果表明，低含量的多聚Q或其他易于聚集的蛋白可以显示出对多聚Q毒性的显著弹性，重复DNA序列的遗传不稳定性可能在不同组织中多聚Q扩展蛋白的进化出现和排斥中发挥了重要作用。由重复CAG DNA序列编码的多谷氨酰胺(PolyQ)蛋白具有多种正常的生物学功能。然而，一些具有异常扩大的PolyQ区域的蛋白质通过未知的机制导致神经退化。为了研究不同的细胞环境是如何调节多Q聚集和毒性的，我们在庞氏裂殖酵母中表达了CAG-展开的亨廷顿蛋白片段。与许多其他真核生物形成鲜明对比的是，S.pombe唯一缺乏含有长多聚Q链的蛋白质。我们的结果表明，尽管S.pombe细胞内源性PolyQ蛋白含量很低，但对PolyQ毒性表现出惊人的、意想不到的弹性，重复DNA序列的遗传不稳定性可能在真核进化中PolyQ结构域的出现和扩展中发挥了重要作用。
Proteins containing polyglutamine (polyQ) regions are found in almost all eukaryotes, albeit with various frequencies. In humans, proteins such as huntingtin (Htt) with abnormally expanded polyQ regions cause neurodegenerative diseases such as Huntington’s disease (HD). To study how the presence of endogenous polyQ aggregation modulates polyQ aggregation and toxicity, we expressed polyQ expanded Htt fragments (polyQ Htt) in Schizosaccharomyces pombe. In stark contrast to other unicellular fungi, such as Saccharomyces cerevisiae, S. pombe is uniquely devoid of proteins with more than 10 Q repeats. We found that polyQ Htt forms aggregates within S. pombe cells only with exceedingly long polyQ expansions. Surprisingly, despite the presence of polyQ Htt aggregates in both the cytoplasm and nucleus, no significant growth defect was observed in S. pombe cells. Further, PCR analysis showed that the repetitive polyQ-encoding DNA region remained constant following transformation and after multiple divisions in S. pombe, in contrast to the genetic instability of polyQ DNA sequences in other organisms. These results demonstrate that cells with a low content of polyQ or other aggregation-prone proteins can show a striking resilience with respect to polyQ toxicity and that genetic instability of repetitive DNA sequences may have played an important role in the evolutionary emergence and exclusion of polyQ expansion proteins in different organisms.IMPORTANCEPolyglutamine (polyQ) proteins encoded by repetitive CAG DNA sequences serve a variety of normal biological functions. Yet some proteins with abnormally expanded polyQ regions cause neurodegeneration through unknown mechanisms. To study how distinct cellular environments modulate polyQ aggregation and toxicity, we expressed CAG-expanded huntingtin fragments in Schizosaccharomyces pombe. In stark contrast to many other eukaryotes, S. pombe is uniquely devoid of proteins containing long polyQ tracts. Our results show that S. pombe cells, despite their low content of endogenous polyQ proteins, exhibit striking and unexpected resilience with respect to polyQ toxicity and that genetic instability of repetitive DNA sequences may have played an important role in the emergence and expansion of polyQ domains in eukaryotic evolution.