Endoplasmic reticulum stress leads to the selective transcriptional downregulation of the glucoamylase gene in Aspergillus niger
Endoplasmic reticulum stress leads to the selective transcriptional downregulation of the glucoamylase gene in Aspergillus niger
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DOI：
10.1111/j.1365-2958.2004.04236.x
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发表时间：
2004-09-01
影响因子：
3.6
通讯作者：
Archer, DB
中科院分区：
文献类型：
--
作者：
Al-Sheikh, H;Watson, AJ;Archer, DB
我们描述了一种新的内质网（ER）相关的应激反应的丝状真菌尼日尔曲霉。ER内的蛋白质折叠的抑制导致细胞反应统称为未折叠蛋白质反应（UPR），我们表明，选择性转录下调的基因编码葡糖淀粉酶，一个主要的分泌蛋白，但不是两个非分泌蛋白，是一个额外的后果ER压力。转录下调的影响是由核运行的研究是在转录水平，而不是mRNA的稳定性，并被发现介导的glaA的启动子在一个区域超过1 kb的翻译开始的上游。ER中蛋白质折叠的抑制可以以多种方式诱导。我们研究了二硫苏糖醇（DTT）的影响，DTT是一种导致未折叠蛋白质形成的还原剂。虽然一般的转录下调被认为与DTT治疗，我们发现，选择性下调与glaA基因相比，非分泌蛋白γ-肌动蛋白和甘油醛3 '-磷酸脱氢酶编码基因观察。DTT处理的真菌细胞还显示出诱导UPR的证据，因为分别编码ER驻留伴侣蛋白和折叠酶的bipA和pdiA的表达被上调，并且hacA（编码负责诱导UPR的转录因子的基因）的剪接发生，从而允许产生活性HacA蛋白。作为研究转录下调效应是否通过HacA（即UPR的一部分）介导的初步尝试，我们检查了通过反义技术诱导的ER应激以降低A.尼日尔.虽然glaA基因在该菌株中的转录被减弱，尼日尔，UPR不明显，表明转录下调机制与UPR不同。
We describe a new endoplasmic reticulum (ER)-associated stress response in the filamentous fungus Aspergillus niger. The inhibition of protein folding within the ER leads to cellular responses known collectively as the unfolded protein response (UPR) and we show that the selective transcriptional downregulation of the gene encoding glucoamylase, a major secreted protein, but not two non-secreted proteins, is an additional consequence of ER stress. The transcriptional downregulation effect is shown by nuclear run-on studies to be at the level of transcription, rather than mRNA stability, and is found to be mediated through the promoter of glaA in a region more than 1 kb upstream of the translational start. The inhibition of protein folding in the ER can be induced in a variety of ways. We examined the effects of dithiothreitol (DTT), a reducing agent that causes the formation of unfolded proteins. Although a general downregulation of transcription was seen with DTT treatment, we show that selective downregulation was observed with the glaA gene compared with genes encoding the non-secreted proteins gamma-actin and glyceraldehyde 3'-phosphate dehydrogenase. The DTT-treated fungal cells also showed evidence for the induction of the UPR because expression of bipA and pdiA, encoding an ER-resident chaperone and foldase, respectively, are upregulated and splicing of hacA, the gene encoding the transcription factor responsible for induction of the UPR, occurs allowing the production of an active HacA protein. As a preliminary attempt to investigate if the transcriptional downregulation effect was mediated through HacA (i.e. part of the UPR), we examined ER stress induced through antisense technology to lower the level of PDI in the ER of A. niger. Although the transcription of glaA was attenuated in that strain of A. niger, UPR was not evident, suggesting that the transcriptional downregulation mechanism is controlled differently from the UPR.