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Nucleolar proteins suppress Caenorhabditis elegans innate immunity by inhibiting p53/CEP-1.

Fuhrman LE, Goel AK, Smith J, Shianna KV, Aballay A - PLoS Genet. (2009)

Bottom Line: Mutation or silencing of NOL-6 and other nucleolar proteins results in an enhanced resistance to bacterial infections.Further studies indicate that the activation of innate immunity by inhibition of nucleolar proteins requires p53/CEP-1 and its transcriptional target SYM-1.Since nucleoli and p53/CEP-1 are conserved, our results reveal an ancient immune mechanism by which the nucleolus may regulate immune responses against bacterial pathogens.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, North Carolina, United States of America.

ABSTRACT
The tumor suppressor p53 has been implicated in multiple functions that play key roles in health and disease, including ribosome biogenesis, control of aging, and cell cycle regulation. A genetic screen for negative regulators of innate immunity in Caenorhabditis elegans led to the identification of a mutation in NOL-6, a nucleolar RNA-associated protein (NRAP), which is involved in ribosome biogenesis and conserved across eukaryotic organisms. Mutation or silencing of NOL-6 and other nucleolar proteins results in an enhanced resistance to bacterial infections. A full-genome microarray analysis on animals with altered immune function due to mutation in nol-6 shows increased transcriptional levels of genes regulated by a p53 homologue, CEP-1. Further studies indicate that the activation of innate immunity by inhibition of nucleolar proteins requires p53/CEP-1 and its transcriptional target SYM-1. Since nucleoli and p53/CEP-1 are conserved, our results reveal an ancient immune mechanism by which the nucleolus may regulate immune responses against bacterial pathogens.

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Related in: MedlinePlus

Derepression of CEP-1 transcriptional activity by nol-6 RNAi activates immunity against S. enterica.(A) Quantitative RT-PCR analysis of 7 cep-1–dependent genes in nematodes grown on dsRNA for vector control or dsRNA for nol-6. Data were analyzed by normalization to pan-actin (act-1,-3,-4) and relative quantification using the comparative-cycle threshold method. Student's exact t test indicates that differences among the groups are significantly different; bar graphs correspond to mean±SEM (n = 3). (B) Wild type and sym-1(mn601) nematodes grown on dsRNA for vector control or dsRNA for nol-6 were fed S. enterica, and the number of live versus dead animals was scored over time. Vector vs. sym-1(mn601): p = 0.0002. For each condition, 60 animals were used. This experiment was performed in duplicate. (C) Wild type and sym-1(mn601) nematodes were fed S. enterica/GFP or S. enterica/GFP for 48 hours, and the percentages of worms exhibiting pharyngeal invasion of S. enterica were quantified. Wild type vs. sym-1(mn601) S. enterica/GFP: p<0.0001. For each condition, approximately 100 animals were used. (D) Mechanism by which disruption of the nucleolus may lead to enhanced resistance to pathogen through the activation of CEP-1. Inhibition of nol-6 and other nucleolar proteins via RNAi or mutation disrupts nucleolar integrity leading to an upregulation of CEP-1-dependent transcription and an increase in resistance to both S. enterica and P. aeruginosa. Disruption of the nucleolus may also lead to enhanced resistance to P. aeruginosa through the activity of PMK-1 and DAF-16.
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pgen-1000657-g006: Derepression of CEP-1 transcriptional activity by nol-6 RNAi activates immunity against S. enterica.(A) Quantitative RT-PCR analysis of 7 cep-1–dependent genes in nematodes grown on dsRNA for vector control or dsRNA for nol-6. Data were analyzed by normalization to pan-actin (act-1,-3,-4) and relative quantification using the comparative-cycle threshold method. Student's exact t test indicates that differences among the groups are significantly different; bar graphs correspond to mean±SEM (n = 3). (B) Wild type and sym-1(mn601) nematodes grown on dsRNA for vector control or dsRNA for nol-6 were fed S. enterica, and the number of live versus dead animals was scored over time. Vector vs. sym-1(mn601): p = 0.0002. For each condition, 60 animals were used. This experiment was performed in duplicate. (C) Wild type and sym-1(mn601) nematodes were fed S. enterica/GFP or S. enterica/GFP for 48 hours, and the percentages of worms exhibiting pharyngeal invasion of S. enterica were quantified. Wild type vs. sym-1(mn601) S. enterica/GFP: p<0.0001. For each condition, approximately 100 animals were used. (D) Mechanism by which disruption of the nucleolus may lead to enhanced resistance to pathogen through the activation of CEP-1. Inhibition of nol-6 and other nucleolar proteins via RNAi or mutation disrupts nucleolar integrity leading to an upregulation of CEP-1-dependent transcription and an increase in resistance to both S. enterica and P. aeruginosa. Disruption of the nucleolus may also lead to enhanced resistance to P. aeruginosa through the activity of PMK-1 and DAF-16.

Mentions: Consistent with the idea that higher CEP-1 activity is responsible for the enhanced immunity against S. enterica of NOL-6-deficient animals, the microarray data show a significant enrichment in CEP-1-regulated genes in rpa-9 mutants (Figure 3E and Table S1). The expression analysis of five studied genes that belong to the cluster of CEP-1-regulated genes that are induced in rpa-9 mutants (Figure 3F) shows that they are also upregulated in nol-6 RNAi nematodes compared to control wild-type nematodes (Figure 6A). An additional known CEP-1 target, egl-1 [61],[62],[63] was also found to be upregulated in nol-6 RNAi nematodes compared to vector control wild-type nematodes (Figure 6A). Taken together, these results suggest that higher CEP-1 activity is responsible for the enhanced resistance to S. enterica-mediated killing in animals with impaired ribosomal function due to mutation or RNAi of nol-6, and suggest that the nucleolus suppresses innate immunity in a CEP-1-dependent manner (Figure 6D).


Nucleolar proteins suppress Caenorhabditis elegans innate immunity by inhibiting p53/CEP-1.

Fuhrman LE, Goel AK, Smith J, Shianna KV, Aballay A - PLoS Genet. (2009)

Derepression of CEP-1 transcriptional activity by nol-6 RNAi activates immunity against S. enterica.(A) Quantitative RT-PCR analysis of 7 cep-1–dependent genes in nematodes grown on dsRNA for vector control or dsRNA for nol-6. Data were analyzed by normalization to pan-actin (act-1,-3,-4) and relative quantification using the comparative-cycle threshold method. Student's exact t test indicates that differences among the groups are significantly different; bar graphs correspond to mean±SEM (n = 3). (B) Wild type and sym-1(mn601) nematodes grown on dsRNA for vector control or dsRNA for nol-6 were fed S. enterica, and the number of live versus dead animals was scored over time. Vector vs. sym-1(mn601): p = 0.0002. For each condition, 60 animals were used. This experiment was performed in duplicate. (C) Wild type and sym-1(mn601) nematodes were fed S. enterica/GFP or S. enterica/GFP for 48 hours, and the percentages of worms exhibiting pharyngeal invasion of S. enterica were quantified. Wild type vs. sym-1(mn601) S. enterica/GFP: p<0.0001. For each condition, approximately 100 animals were used. (D) Mechanism by which disruption of the nucleolus may lead to enhanced resistance to pathogen through the activation of CEP-1. Inhibition of nol-6 and other nucleolar proteins via RNAi or mutation disrupts nucleolar integrity leading to an upregulation of CEP-1-dependent transcription and an increase in resistance to both S. enterica and P. aeruginosa. Disruption of the nucleolus may also lead to enhanced resistance to P. aeruginosa through the activity of PMK-1 and DAF-16.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2734340&req=5

pgen-1000657-g006: Derepression of CEP-1 transcriptional activity by nol-6 RNAi activates immunity against S. enterica.(A) Quantitative RT-PCR analysis of 7 cep-1–dependent genes in nematodes grown on dsRNA for vector control or dsRNA for nol-6. Data were analyzed by normalization to pan-actin (act-1,-3,-4) and relative quantification using the comparative-cycle threshold method. Student's exact t test indicates that differences among the groups are significantly different; bar graphs correspond to mean±SEM (n = 3). (B) Wild type and sym-1(mn601) nematodes grown on dsRNA for vector control or dsRNA for nol-6 were fed S. enterica, and the number of live versus dead animals was scored over time. Vector vs. sym-1(mn601): p = 0.0002. For each condition, 60 animals were used. This experiment was performed in duplicate. (C) Wild type and sym-1(mn601) nematodes were fed S. enterica/GFP or S. enterica/GFP for 48 hours, and the percentages of worms exhibiting pharyngeal invasion of S. enterica were quantified. Wild type vs. sym-1(mn601) S. enterica/GFP: p<0.0001. For each condition, approximately 100 animals were used. (D) Mechanism by which disruption of the nucleolus may lead to enhanced resistance to pathogen through the activation of CEP-1. Inhibition of nol-6 and other nucleolar proteins via RNAi or mutation disrupts nucleolar integrity leading to an upregulation of CEP-1-dependent transcription and an increase in resistance to both S. enterica and P. aeruginosa. Disruption of the nucleolus may also lead to enhanced resistance to P. aeruginosa through the activity of PMK-1 and DAF-16.
Mentions: Consistent with the idea that higher CEP-1 activity is responsible for the enhanced immunity against S. enterica of NOL-6-deficient animals, the microarray data show a significant enrichment in CEP-1-regulated genes in rpa-9 mutants (Figure 3E and Table S1). The expression analysis of five studied genes that belong to the cluster of CEP-1-regulated genes that are induced in rpa-9 mutants (Figure 3F) shows that they are also upregulated in nol-6 RNAi nematodes compared to control wild-type nematodes (Figure 6A). An additional known CEP-1 target, egl-1 [61],[62],[63] was also found to be upregulated in nol-6 RNAi nematodes compared to vector control wild-type nematodes (Figure 6A). Taken together, these results suggest that higher CEP-1 activity is responsible for the enhanced resistance to S. enterica-mediated killing in animals with impaired ribosomal function due to mutation or RNAi of nol-6, and suggest that the nucleolus suppresses innate immunity in a CEP-1-dependent manner (Figure 6D).

Bottom Line: Mutation or silencing of NOL-6 and other nucleolar proteins results in an enhanced resistance to bacterial infections.Further studies indicate that the activation of innate immunity by inhibition of nucleolar proteins requires p53/CEP-1 and its transcriptional target SYM-1.Since nucleoli and p53/CEP-1 are conserved, our results reveal an ancient immune mechanism by which the nucleolus may regulate immune responses against bacterial pathogens.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, North Carolina, United States of America.

ABSTRACT
The tumor suppressor p53 has been implicated in multiple functions that play key roles in health and disease, including ribosome biogenesis, control of aging, and cell cycle regulation. A genetic screen for negative regulators of innate immunity in Caenorhabditis elegans led to the identification of a mutation in NOL-6, a nucleolar RNA-associated protein (NRAP), which is involved in ribosome biogenesis and conserved across eukaryotic organisms. Mutation or silencing of NOL-6 and other nucleolar proteins results in an enhanced resistance to bacterial infections. A full-genome microarray analysis on animals with altered immune function due to mutation in nol-6 shows increased transcriptional levels of genes regulated by a p53 homologue, CEP-1. Further studies indicate that the activation of innate immunity by inhibition of nucleolar proteins requires p53/CEP-1 and its transcriptional target SYM-1. Since nucleoli and p53/CEP-1 are conserved, our results reveal an ancient immune mechanism by which the nucleolus may regulate immune responses against bacterial pathogens.

Show MeSH
Related in: MedlinePlus