5-fluorocytosine resistance is associated with hypermutation and alterations in capsule biosynthesis in Cryptococcus
5-fluorocytosine resistance is associated with hypermutation and alterations in capsule biosynthesis in Cryptococcus
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DOI：
10.1038/s41467-019-13890-z
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发表时间：
2020-01-08
影响因子：
16.6
通讯作者：
Heitman, Joseph
中科院分区：
文献类型：
--
作者：
Billmyre, R. Blake;Clancey, Shelly Applen;Heitman, Joseph
感染真菌病原体隐球菌的患者用5-氟胞嘧啶（5 FC）和阿替霉素B的组合治疗最有效。5 FC作为前药，在真菌细胞摄取后转化为毒性5-氟尿嘧啶（5 FU）。然而，病原体经常通过不清楚的机制产生耐药性。在这里，我们表明，耐药的5 FC在隐球菌deuterogattii获得更频繁的分离与缺陷的DNA错配修复，赋予一个升高的突变率。我们使用16个独立的分离株的全基因组测序来鉴定与体外5 FC耐药相关的突变。我们发现已知的耐药基因（FUR 1和FCY 2）和基因UXS 1中的突变，以前显示编码一种酶，将UDP-葡萄糖醛酸转化为UDP-木糖用于胶囊生物合成，但不知道在5 FC代谢中发挥作用。UXS 1的突变导致UDP-葡萄糖醛酸的积累和核苷酸代谢的改变，这似乎抑制了5 FC及其毒性衍生物5 FU的毒性。
Patients infected with the fungal pathogen Cryptococcus are most effectively treated with a combination of 5-fluorocytosine (5FC) and amphotericin B. 5FC acts as a prodrug, which is converted into toxic 5-fluorouracil (5FU) upon uptake into fungal cells. However, the pathogen frequently develops resistance through unclear mechanisms. Here we show that resistance to 5FC in Cryptococcus deuterogattii is acquired more frequently in isolates with defects in DNA mismatch repair that confer an elevated mutation rate. We use whole genome sequencing of 16 independent isolates to identify mutations associated with 5FC resistance in vitro. We find mutations in known resistance genes (FUR1 and FCY2) and in a gene UXS1, previously shown to encode an enzyme that converts UDP-glucuronic acid to UDP-xylose for capsule biosynthesis, but not known to play a role in 5FC metabolism. Mutations in UXS1 lead to accumulation of UDP-glucuronic acid and alterations in nucleotide metabolism, which appear to suppress toxicity of both 5FC and its toxic derivative 5FU.