Association with AflR in endosomes reveals new functions for AflJ in aflatoxin biosynthesis.
Association with AflR in endosomes reveals new functions for AflJ in aflatoxin biosynthesis.
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作者：
Ehrlich KC;Mack BM;Wei Q;Li P;Roze LV;Dazzo F;Cary JW;Bhatnagar D;Linz JE
黄曲霉毒素是真菌来源的最有效的天然致癌物。黄曲霉毒素的生物合成涉及超过25个基因的协调表达。黄曲霉毒素基因簇中的一个基因aflJ的功能尚未完全了解，但是，由于先前的研究证明了Zn2Cys6转录因子AflR和AflJ之间的物理相互作用，因此提出AflJ充当转录共激活因子。图像分析显示，在A.寄生虫，内体群集在细胞内和隔膜附近。AflJ与黄色荧光蛋白融合，互补了A. parasiticus ΔaflJ主要定位于核内体。我们发现AflJ与AflR共定位于核内体和核中。染色质免疫沉淀没有检测到AflJ在已知AflR DNA识别位点的结合，表明AflJ不结合这些位点或瞬时结合这些位点。基于这些数据，我们假设AflJ协助AflR转运到细胞核或从细胞核转运，从而控制AflR用于黄曲霉毒素生物合成簇基因的转录激活的可用性。AflJ还可以帮助将内体引导至细胞质膜以用于黄曲霉毒素输出。
Aflatoxins are the most potent naturally occurring carcinogens of fungal origin. Biosynthesis of aflatoxin involves the coordinated expression of more than 25 genes. The function of one gene in the aflatoxin gene cluster, aflJ, is not entirely understood but, because previous studies demonstrated a physical interaction between the Zn2Cys6 transcription factor AflR and AflJ, AflJ was proposed to act as a transcriptional co-activator. Image analysis revealed that, in the absence of aflJ in A. parasiticus, endosomes cluster within cells and near septa. AflJ fused to yellow fluorescent protein complemented the mutation in A. parasiticus ΔaflJ and localized mainly in endosomes. We found that AflJ co-localizes with AflR both in endosomes and in nuclei. Chromatin immunoprecipitation did not detect AflJ binding at known AflR DNA recognition sites suggesting that AflJ either does not bind to these sites or binds to them transiently. Based on these data, we hypothesize that AflJ assists in AflR transport to or from the nucleus, thus controlling the availability of AflR for transcriptional activation of aflatoxin biosynthesis cluster genes. AflJ may also assist in directing endosomes to the cytoplasmic membrane for aflatoxin export.
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