H4K5去乙酰化对镍胁迫下酿酒酵母细胞壁完整性途径的调控作用

H4K5 deacetylation regulates cell wall integrity pathway in Saccharomyces cerevisiae exposed to nickel stress

摘要:

【目的】金属镍(nickel, Ni)是人类广泛接触的重金属污染物之一,镍暴露会激活细胞内的细胞壁完整性(cell wall integrity, CWI)信号通路,也会导致细胞内组蛋白乙酰化水平降低,但CWI途径在镍胁迫时是否受组蛋白乙酰化调控尚不完全清楚。【方法】利用组蛋白定点突变型菌株H4K5R (模拟去乙酰化状态),分析镍胁迫下H4K5去乙酰化对酿酒酵母CWI途径的调控作用【结果】与野生型菌株相比,定点突变型菌株H4K5R具有较强的镍抗性:在5.0 mmol/L NiCl₂胁迫下,定点突变型菌株仍能生长良好;Western blotting与qRT-PCR结果表明,野生型菌株BY4741在5.0 mmol/L NiCl₂胁迫下细胞壁完整性途径被激活,甘露聚糖与葡聚糖调控基因Mnn9表达量显著上调3.13倍、Fks1表达量显著上调1.49倍,甘露聚糖、β-葡聚糖的含量也增加,说明此时野生型菌株激活了CWI途径,细胞壁成分含量增加;定点突变型菌株H4K5R在5.0 mmol/L NiCl₂胁迫下CWI途径激活程度较轻,虽然Mnn9、Fks1表达量上调,但甘露聚糖含量变化并不显著,而相较于野生型菌株β-葡聚糖含量增加幅度较小。【结论】在5.0 mmol/L NiCl₂胁迫下,定点突变型菌株H4K5位点的去乙酰化调控CWI途径,进而影响细胞壁组分的变化。

Abstract:

[Objective] Nickel (Ni) is one of the heavy metal pollutants to which humans are widely exposed, and nickel exposure activates the cell wall integrity (CWI) signaling pathway, which lowers the level of intracellular histone acetylation. However, whether the CWI pathway is regulated by histone acetylation under nickel stress remains to be fully understood. [Methods] We used the histone-targeted mutant strain H4K5R (mimicking the deacetylated state) to study the regulation of the CWI pathway in Saccharomyces cerevisiae by H4K5 deacetylation under nickel stress, aiming to lay a foundation for unveiling the regulatory role of histone modifications in eukaryotes in response to heavy metal stress. [Results] Compared with the wildtype strain, H4K5R had strong nickel resistance, being able to grow in the presence of 5.0 mmol/L NiCl₂. The results of Western blotting and qRT-PCR showed that the CWI pathway of the wildtype strain BY4741 was activated under 5.0 mmol/L NiCl₂, with the expression of Mnn9 (encoding α-1,6-mannosyl transferase) and Fks1 (encoding glucan synthase) being up-regulated by 3.13 folds and 1.49 folds, respectively. Moreover, the content of mannan and β-glucan were increased, which indicated that the wildtype strain activated the CWI pathway to increase the content of cell wall component. The activation of the CWI pathway in H4K5R was mild under the stress of 5.0 mmol/L NiCl₂. Although the expression of Mnn9 and Fks1 was up-regulated, the changes in mannan content were not significant, and the increase in β-glucan content was less than that of the wildtype strain. [Conclusion] Under 5.0 mmol/L NiCl₂ stress, the deacetylation of H4K5 in the mutant strain regulated the CWI pathway, which affected the changes in cell wall components.