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The Candida albicans Histone Acetyltransferase Hat1 Regulates Stress Resistance and Virulence via Distinct Chromatin Assembly Pathways.

Tscherner M, Zwolanek F, Je S, Sedlazeck FJ, Petryshyn A, Frohner IE, Mavrianos J, Chauhan N, von Haeseler A, Kuchler K - PLoS Pathog. (2015)

Bottom Line: Hydrogen peroxide resistance in cells lacking Hat1 results from higher induction rates of oxidative stress gene expression, accompanied by reduced histone density as well as subsequent increased RNA polymerase recruitment.Remarkably, the oxidative stress phenotype of hat1Δ/Δ cells is a species-specific trait only found in C. albicans and members of the CTG clade.The reduced azole susceptibility appears to be conserved in a wider range of fungi.

View Article: PubMed Central - PubMed

Affiliation: Department for Medical Biochemistry, Medical University of Vienna, Max F. Perutz Laboratories, Campus Vienna Biocenter, Vienna, Austria.

ABSTRACT
Human fungal pathogens like Candida albicans respond to host immune surveillance by rapidly adapting their transcriptional programs. Chromatin assembly factors are involved in the regulation of stress genes by modulating the histone density at these loci. Here, we report a novel role for the chromatin assembly-associated histone acetyltransferase complex NuB4 in regulating oxidative stress resistance, antifungal drug tolerance and virulence in C. albicans. Strikingly, depletion of the NuB4 catalytic subunit, the histone acetyltransferase Hat1, markedly increases resistance to oxidative stress and tolerance to azole antifungals. Hydrogen peroxide resistance in cells lacking Hat1 results from higher induction rates of oxidative stress gene expression, accompanied by reduced histone density as well as subsequent increased RNA polymerase recruitment. Furthermore, hat1Δ/Δ cells, despite showing growth defects in vitro, display reduced susceptibility to reactive oxygen-mediated killing by innate immune cells. Thus, clearance from infected mice is delayed although cells lacking Hat1 are severely compromised in killing the host. Interestingly, increased oxidative stress resistance and azole tolerance are phenocopied by the loss of histone chaperone complexes CAF-1 and HIR, respectively, suggesting a central role for NuB4 in the delivery of histones destined for chromatin assembly via distinct pathways. Remarkably, the oxidative stress phenotype of hat1Δ/Δ cells is a species-specific trait only found in C. albicans and members of the CTG clade. The reduced azole susceptibility appears to be conserved in a wider range of fungi. Thus, our work demonstrates how highly conserved chromatin assembly pathways can acquire new functions in pathogenic fungi during coevolution with the host.

No MeSH data available.


Related in: MedlinePlus

Higher ROS detoxification capacity of hat1Δ/Δ cells causes resistance to neutrophil killing.(A) Superoxide dismutases Sod4 and Sod5 are induced in hat1Δ/Δ cells. Expression levels of SOD4 and SOD5 in logarithmically growing cells were detected by RT-qPCR. Transcript levels were normalized to the expression level of the reference gene (RG) RIP1. Data are shown as mean + SD from 3 independent experiments. (B) Infection of macrophages with hat1Δ/Δ cells causes reduced ROS accumulation. ROS levels were determined by measuring luminol-dependent chemiluminescence [relative luciferase units (RLU) min-1 per 1000 immune cells] in 2.5 min intervals during interaction of the indicated C. albicans strains with bone marrow-derived murine macrophages (BMDMs). One representative experiment is shown. Data were reproduced in three independent experiments. (C) Quantification of total ROS release upon interaction with BMDMs. Experiment was performed as described in (B). The area under the curve within 90 min of interaction was calculated. Data are shown as mean + SD from three independent experiments. (D) Cells lacking Hat1 show increased survival to neutrophil killing. Survival of C. albicans cells upon one hour interaction with murine bone marrow neutrophils was determined by plating and CFU counting. Data are shown as mean + SD from three independent experiments. (A-D) *P<0.05, **P<0.01 relative to the wild-type (Student's t-test).
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ppat.1005218.g008: Higher ROS detoxification capacity of hat1Δ/Δ cells causes resistance to neutrophil killing.(A) Superoxide dismutases Sod4 and Sod5 are induced in hat1Δ/Δ cells. Expression levels of SOD4 and SOD5 in logarithmically growing cells were detected by RT-qPCR. Transcript levels were normalized to the expression level of the reference gene (RG) RIP1. Data are shown as mean + SD from 3 independent experiments. (B) Infection of macrophages with hat1Δ/Δ cells causes reduced ROS accumulation. ROS levels were determined by measuring luminol-dependent chemiluminescence [relative luciferase units (RLU) min-1 per 1000 immune cells] in 2.5 min intervals during interaction of the indicated C. albicans strains with bone marrow-derived murine macrophages (BMDMs). One representative experiment is shown. Data were reproduced in three independent experiments. (C) Quantification of total ROS release upon interaction with BMDMs. Experiment was performed as described in (B). The area under the curve within 90 min of interaction was calculated. Data are shown as mean + SD from three independent experiments. (D) Cells lacking Hat1 show increased survival to neutrophil killing. Survival of C. albicans cells upon one hour interaction with murine bone marrow neutrophils was determined by plating and CFU counting. Data are shown as mean + SD from three independent experiments. (A-D) *P<0.05, **P<0.01 relative to the wild-type (Student's t-test).

Mentions: The absence of Hat1 and Cac2 leads to upregulation of oxidative stress genes and resistance to hydrogen peroxide. ROS are produced by immune cells to kill C. albicans during the infection process. The fungus counteracts this attack by upregulating ROS detoxifying enzymes of which the superoxide dismutases Sod5 and to some extend Sod4 were shown be essential for survival of C. albicans upon phagocytosis [26]. Interestingly, our RNA-Seq data not only revealed an upregulation of the catalase and glutathione-utilizing enzymes, but also markedly increased expression of genes encoding the superoxide dismutases Sod4 and Sod5 in cells lacking Hat1. The significant induction of SOD4 and SOD5 in the hat1Δ/Δ strain was also confirmed by RT-qPCR analysis (Fig 8A).


The Candida albicans Histone Acetyltransferase Hat1 Regulates Stress Resistance and Virulence via Distinct Chromatin Assembly Pathways.

Tscherner M, Zwolanek F, Je S, Sedlazeck FJ, Petryshyn A, Frohner IE, Mavrianos J, Chauhan N, von Haeseler A, Kuchler K - PLoS Pathog. (2015)

Higher ROS detoxification capacity of hat1Δ/Δ cells causes resistance to neutrophil killing.(A) Superoxide dismutases Sod4 and Sod5 are induced in hat1Δ/Δ cells. Expression levels of SOD4 and SOD5 in logarithmically growing cells were detected by RT-qPCR. Transcript levels were normalized to the expression level of the reference gene (RG) RIP1. Data are shown as mean + SD from 3 independent experiments. (B) Infection of macrophages with hat1Δ/Δ cells causes reduced ROS accumulation. ROS levels were determined by measuring luminol-dependent chemiluminescence [relative luciferase units (RLU) min-1 per 1000 immune cells] in 2.5 min intervals during interaction of the indicated C. albicans strains with bone marrow-derived murine macrophages (BMDMs). One representative experiment is shown. Data were reproduced in three independent experiments. (C) Quantification of total ROS release upon interaction with BMDMs. Experiment was performed as described in (B). The area under the curve within 90 min of interaction was calculated. Data are shown as mean + SD from three independent experiments. (D) Cells lacking Hat1 show increased survival to neutrophil killing. Survival of C. albicans cells upon one hour interaction with murine bone marrow neutrophils was determined by plating and CFU counting. Data are shown as mean + SD from three independent experiments. (A-D) *P<0.05, **P<0.01 relative to the wild-type (Student's t-test).
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ppat.1005218.g008: Higher ROS detoxification capacity of hat1Δ/Δ cells causes resistance to neutrophil killing.(A) Superoxide dismutases Sod4 and Sod5 are induced in hat1Δ/Δ cells. Expression levels of SOD4 and SOD5 in logarithmically growing cells were detected by RT-qPCR. Transcript levels were normalized to the expression level of the reference gene (RG) RIP1. Data are shown as mean + SD from 3 independent experiments. (B) Infection of macrophages with hat1Δ/Δ cells causes reduced ROS accumulation. ROS levels were determined by measuring luminol-dependent chemiluminescence [relative luciferase units (RLU) min-1 per 1000 immune cells] in 2.5 min intervals during interaction of the indicated C. albicans strains with bone marrow-derived murine macrophages (BMDMs). One representative experiment is shown. Data were reproduced in three independent experiments. (C) Quantification of total ROS release upon interaction with BMDMs. Experiment was performed as described in (B). The area under the curve within 90 min of interaction was calculated. Data are shown as mean + SD from three independent experiments. (D) Cells lacking Hat1 show increased survival to neutrophil killing. Survival of C. albicans cells upon one hour interaction with murine bone marrow neutrophils was determined by plating and CFU counting. Data are shown as mean + SD from three independent experiments. (A-D) *P<0.05, **P<0.01 relative to the wild-type (Student's t-test).
Mentions: The absence of Hat1 and Cac2 leads to upregulation of oxidative stress genes and resistance to hydrogen peroxide. ROS are produced by immune cells to kill C. albicans during the infection process. The fungus counteracts this attack by upregulating ROS detoxifying enzymes of which the superoxide dismutases Sod5 and to some extend Sod4 were shown be essential for survival of C. albicans upon phagocytosis [26]. Interestingly, our RNA-Seq data not only revealed an upregulation of the catalase and glutathione-utilizing enzymes, but also markedly increased expression of genes encoding the superoxide dismutases Sod4 and Sod5 in cells lacking Hat1. The significant induction of SOD4 and SOD5 in the hat1Δ/Δ strain was also confirmed by RT-qPCR analysis (Fig 8A).

Bottom Line: Hydrogen peroxide resistance in cells lacking Hat1 results from higher induction rates of oxidative stress gene expression, accompanied by reduced histone density as well as subsequent increased RNA polymerase recruitment.Remarkably, the oxidative stress phenotype of hat1Δ/Δ cells is a species-specific trait only found in C. albicans and members of the CTG clade.The reduced azole susceptibility appears to be conserved in a wider range of fungi.

View Article: PubMed Central - PubMed

Affiliation: Department for Medical Biochemistry, Medical University of Vienna, Max F. Perutz Laboratories, Campus Vienna Biocenter, Vienna, Austria.

ABSTRACT
Human fungal pathogens like Candida albicans respond to host immune surveillance by rapidly adapting their transcriptional programs. Chromatin assembly factors are involved in the regulation of stress genes by modulating the histone density at these loci. Here, we report a novel role for the chromatin assembly-associated histone acetyltransferase complex NuB4 in regulating oxidative stress resistance, antifungal drug tolerance and virulence in C. albicans. Strikingly, depletion of the NuB4 catalytic subunit, the histone acetyltransferase Hat1, markedly increases resistance to oxidative stress and tolerance to azole antifungals. Hydrogen peroxide resistance in cells lacking Hat1 results from higher induction rates of oxidative stress gene expression, accompanied by reduced histone density as well as subsequent increased RNA polymerase recruitment. Furthermore, hat1Δ/Δ cells, despite showing growth defects in vitro, display reduced susceptibility to reactive oxygen-mediated killing by innate immune cells. Thus, clearance from infected mice is delayed although cells lacking Hat1 are severely compromised in killing the host. Interestingly, increased oxidative stress resistance and azole tolerance are phenocopied by the loss of histone chaperone complexes CAF-1 and HIR, respectively, suggesting a central role for NuB4 in the delivery of histones destined for chromatin assembly via distinct pathways. Remarkably, the oxidative stress phenotype of hat1Δ/Δ cells is a species-specific trait only found in C. albicans and members of the CTG clade. The reduced azole susceptibility appears to be conserved in a wider range of fungi. Thus, our work demonstrates how highly conserved chromatin assembly pathways can acquire new functions in pathogenic fungi during coevolution with the host.

No MeSH data available.


Related in: MedlinePlus