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Hyphal development in Candida albicans requires two temporally linked changes in promoter chromatin for initiation and maintenance.

Lu Y, Su C, Wang A, Liu H - PLoS Biol. (2011)

Bottom Line: Although many regulators have been found involved in hyphal development, the mechanisms of regulating hyphal development and plasticity of dimorphism remain unclear.Maintenance requires promoter recruitment of Hda1 histone deacetylase under reduced Tor1 (target of rapamycin) signaling.Such temporally linked regulation of promoter chromatin by different signaling pathways provides a unique mechanism for integrating multiple signals during development and cell fate specification.

View Article: PubMed Central - PubMed

Affiliation: Department of Biological Chemistry, University of California, Irvine, California, United States of America.

ABSTRACT
Phenotypic plasticity is common in development. For Candida albicans, the most common cause of invasive fungal infections in humans, morphological plasticity is its defining feature and is critical for its pathogenesis. Unlike other fungal pathogens that exist primarily in either yeast or hyphal forms, C. albicans is able to switch reversibly between yeast and hyphal growth forms in response to environmental cues. Although many regulators have been found involved in hyphal development, the mechanisms of regulating hyphal development and plasticity of dimorphism remain unclear. Here we show that hyphal development involves two sequential regulations of the promoter chromatin of hypha-specific genes. Initiation requires a rapid but temporary disappearance of the Nrg1 transcriptional repressor of hyphal morphogenesis via activation of the cAMP-PKA pathway. Maintenance requires promoter recruitment of Hda1 histone deacetylase under reduced Tor1 (target of rapamycin) signaling. Hda1 deacetylates a subunit of the NuA4 histone acetyltransferase module, leading to eviction of the NuA4 acetyltransferase module and blockage of Nrg1 access to promoters of hypha-specific genes. Promoter recruitment of Hda1 for hyphal maintenance happens only during the period when Nrg1 is gone. The sequential regulation of hyphal development by the activation of the cAMP-PKA pathway and reduced Tor1 signaling provides a molecular mechanism for plasticity of dimorphism and how C. albicans adapts to the varied host environments in pathogenesis. Such temporally linked regulation of promoter chromatin by different signaling pathways provides a unique mechanism for integrating multiple signals during development and cell fate specification.

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Promoter recruitment of Hda1 is required for hyphal maintenance by inhibiting Nrg1 access to the promoters of hypha-specific genes.(A, B) Hda1 is required for maintenance of hyphal development as shown by morphology and expression levels of hypha-specific genes during hyphal induction. Cells of wild-type (TS3.3+pBES116) and hda1/hda1 (HLY4032+pBES116) strains were diluted into YPD with 10% serum at 37°C. HWP1, ALS3, and ECE1 mRNA levels were determined by qRT-PCR. The signal obtained from ACT1 mRNA was used as a loading control for normalization. (C) Nrg1-Myc binds the promoters of hypha-specific genes in hda1 cells during hyphal elongation in YPD with 10% serum. (D) Serum-dependent binding of Hda1-Myc to the hyphal promoters in wild-type cells during hyphal induction. Cells of wild-type strain containing Hda1-Myc (HLY4033) were diluted into pre-warmed YPD medium at 37°C in the presence or absence of 10% serum. ChIP DNA in (C, D) were quantitated by qPCR with primers at the UAS regions of hypha-specific genes as described in Figure 1. Data for ALS3 and ECE1 from (B, C, D) are shown in Figure S2. All data show the average of three independent qRT-PCR or qPCR experiments with error bars representing the SEM.
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pbio-1001105-g003: Promoter recruitment of Hda1 is required for hyphal maintenance by inhibiting Nrg1 access to the promoters of hypha-specific genes.(A, B) Hda1 is required for maintenance of hyphal development as shown by morphology and expression levels of hypha-specific genes during hyphal induction. Cells of wild-type (TS3.3+pBES116) and hda1/hda1 (HLY4032+pBES116) strains were diluted into YPD with 10% serum at 37°C. HWP1, ALS3, and ECE1 mRNA levels were determined by qRT-PCR. The signal obtained from ACT1 mRNA was used as a loading control for normalization. (C) Nrg1-Myc binds the promoters of hypha-specific genes in hda1 cells during hyphal elongation in YPD with 10% serum. (D) Serum-dependent binding of Hda1-Myc to the hyphal promoters in wild-type cells during hyphal induction. Cells of wild-type strain containing Hda1-Myc (HLY4033) were diluted into pre-warmed YPD medium at 37°C in the presence or absence of 10% serum. ChIP DNA in (C, D) were quantitated by qPCR with primers at the UAS regions of hypha-specific genes as described in Figure 1. Data for ALS3 and ECE1 from (B, C, D) are shown in Figure S2. All data show the average of three independent qRT-PCR or qPCR experiments with error bars representing the SEM.

Mentions: One possible mechanism for the reduced promoter access by Nrg1 during hyphal elongation is a change in promoter chromatin. C. albicans has one class II HDAC Hda1 that functions as a repressor for phenotypic switching [54]. We found that cells deleted of HDA1 were unable to maintain hyphal growth. They were impaired in sustained hyphal development and transcription of hypha-specific genes, but had no detectable defects during initial germ-tube formation (Figures 3AB, S2A and Table S1A). Furthermore, levels of promoter-bound Nrg1 increased dramatically in the hda1 mutant after hyphal initiation, suggesting that Hda1 is required to prevent Nrg1 binding to the promoters for sustained hyphal growth (Figures 3C and S2B). These observations of the hda1 mutant are similar to that of wild-type cells inoculated into rich medium at 37°C without serum (Figure 1). To determine whether Hda1 functions directly on the promoters of hypha-specific genes, we performed a time course ChIP of Hda1. We found that Hda1 was recruited to the promoters during hyphal induction in a serum-dependent manner (Figures 3D and S2C). We suggest that serum-induced Hda1 recruitment to the promoters of hypha-specific genes leads to a change in promoter chromatin that is no longer accessible to Nrg1, leading to sustained hyphal development.


Hyphal development in Candida albicans requires two temporally linked changes in promoter chromatin for initiation and maintenance.

Lu Y, Su C, Wang A, Liu H - PLoS Biol. (2011)

Promoter recruitment of Hda1 is required for hyphal maintenance by inhibiting Nrg1 access to the promoters of hypha-specific genes.(A, B) Hda1 is required for maintenance of hyphal development as shown by morphology and expression levels of hypha-specific genes during hyphal induction. Cells of wild-type (TS3.3+pBES116) and hda1/hda1 (HLY4032+pBES116) strains were diluted into YPD with 10% serum at 37°C. HWP1, ALS3, and ECE1 mRNA levels were determined by qRT-PCR. The signal obtained from ACT1 mRNA was used as a loading control for normalization. (C) Nrg1-Myc binds the promoters of hypha-specific genes in hda1 cells during hyphal elongation in YPD with 10% serum. (D) Serum-dependent binding of Hda1-Myc to the hyphal promoters in wild-type cells during hyphal induction. Cells of wild-type strain containing Hda1-Myc (HLY4033) were diluted into pre-warmed YPD medium at 37°C in the presence or absence of 10% serum. ChIP DNA in (C, D) were quantitated by qPCR with primers at the UAS regions of hypha-specific genes as described in Figure 1. Data for ALS3 and ECE1 from (B, C, D) are shown in Figure S2. All data show the average of three independent qRT-PCR or qPCR experiments with error bars representing the SEM.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3139633&req=5

pbio-1001105-g003: Promoter recruitment of Hda1 is required for hyphal maintenance by inhibiting Nrg1 access to the promoters of hypha-specific genes.(A, B) Hda1 is required for maintenance of hyphal development as shown by morphology and expression levels of hypha-specific genes during hyphal induction. Cells of wild-type (TS3.3+pBES116) and hda1/hda1 (HLY4032+pBES116) strains were diluted into YPD with 10% serum at 37°C. HWP1, ALS3, and ECE1 mRNA levels were determined by qRT-PCR. The signal obtained from ACT1 mRNA was used as a loading control for normalization. (C) Nrg1-Myc binds the promoters of hypha-specific genes in hda1 cells during hyphal elongation in YPD with 10% serum. (D) Serum-dependent binding of Hda1-Myc to the hyphal promoters in wild-type cells during hyphal induction. Cells of wild-type strain containing Hda1-Myc (HLY4033) were diluted into pre-warmed YPD medium at 37°C in the presence or absence of 10% serum. ChIP DNA in (C, D) were quantitated by qPCR with primers at the UAS regions of hypha-specific genes as described in Figure 1. Data for ALS3 and ECE1 from (B, C, D) are shown in Figure S2. All data show the average of three independent qRT-PCR or qPCR experiments with error bars representing the SEM.
Mentions: One possible mechanism for the reduced promoter access by Nrg1 during hyphal elongation is a change in promoter chromatin. C. albicans has one class II HDAC Hda1 that functions as a repressor for phenotypic switching [54]. We found that cells deleted of HDA1 were unable to maintain hyphal growth. They were impaired in sustained hyphal development and transcription of hypha-specific genes, but had no detectable defects during initial germ-tube formation (Figures 3AB, S2A and Table S1A). Furthermore, levels of promoter-bound Nrg1 increased dramatically in the hda1 mutant after hyphal initiation, suggesting that Hda1 is required to prevent Nrg1 binding to the promoters for sustained hyphal growth (Figures 3C and S2B). These observations of the hda1 mutant are similar to that of wild-type cells inoculated into rich medium at 37°C without serum (Figure 1). To determine whether Hda1 functions directly on the promoters of hypha-specific genes, we performed a time course ChIP of Hda1. We found that Hda1 was recruited to the promoters during hyphal induction in a serum-dependent manner (Figures 3D and S2C). We suggest that serum-induced Hda1 recruitment to the promoters of hypha-specific genes leads to a change in promoter chromatin that is no longer accessible to Nrg1, leading to sustained hyphal development.

Bottom Line: Although many regulators have been found involved in hyphal development, the mechanisms of regulating hyphal development and plasticity of dimorphism remain unclear.Maintenance requires promoter recruitment of Hda1 histone deacetylase under reduced Tor1 (target of rapamycin) signaling.Such temporally linked regulation of promoter chromatin by different signaling pathways provides a unique mechanism for integrating multiple signals during development and cell fate specification.

View Article: PubMed Central - PubMed

Affiliation: Department of Biological Chemistry, University of California, Irvine, California, United States of America.

ABSTRACT
Phenotypic plasticity is common in development. For Candida albicans, the most common cause of invasive fungal infections in humans, morphological plasticity is its defining feature and is critical for its pathogenesis. Unlike other fungal pathogens that exist primarily in either yeast or hyphal forms, C. albicans is able to switch reversibly between yeast and hyphal growth forms in response to environmental cues. Although many regulators have been found involved in hyphal development, the mechanisms of regulating hyphal development and plasticity of dimorphism remain unclear. Here we show that hyphal development involves two sequential regulations of the promoter chromatin of hypha-specific genes. Initiation requires a rapid but temporary disappearance of the Nrg1 transcriptional repressor of hyphal morphogenesis via activation of the cAMP-PKA pathway. Maintenance requires promoter recruitment of Hda1 histone deacetylase under reduced Tor1 (target of rapamycin) signaling. Hda1 deacetylates a subunit of the NuA4 histone acetyltransferase module, leading to eviction of the NuA4 acetyltransferase module and blockage of Nrg1 access to promoters of hypha-specific genes. Promoter recruitment of Hda1 for hyphal maintenance happens only during the period when Nrg1 is gone. The sequential regulation of hyphal development by the activation of the cAMP-PKA pathway and reduced Tor1 signaling provides a molecular mechanism for plasticity of dimorphism and how C. albicans adapts to the varied host environments in pathogenesis. Such temporally linked regulation of promoter chromatin by different signaling pathways provides a unique mechanism for integrating multiple signals during development and cell fate specification.

Show MeSH
Related in: MedlinePlus