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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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Nucleolar protein knockdown activates immunity against S. enterica in a p53/cep-1–dependent manner.(A) Wild type and rpa-9 nematodes were fed S. enterica on plates containing either 0.005 µg/mL actinomycin D or buffer. Wild type vs. Wild type+Act. D: p = 0.0261. (B) Wild type nematodes were grown on dsRNA for vector control or dsRNA for rps genes, and the number of living nematodes was scored after five days of feeding on S. enterica. Differences between vector and rps RNAi was statistically significant in all cases, p<0.0001. (C) Wild type and cep-1(gk138) nematodes were grown on dsRNA for vector control, dsRNA for nol-6, or dsRNA for rps genes, and the number of live versus dead animals was scored over time. Wild type vs. nol-6 RNAi: p<0.0001. Wild type vs. cep-1(gk138);nol-6 RNAi: p>0.05. Since cep-1(gk138) nematodes exhibit an Egl phenotype, the animals that die from matricide were censored. For each condition, 57–61 animals were used.
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pgen-1000657-g005: Nucleolar protein knockdown activates immunity against S. enterica in a p53/cep-1–dependent manner.(A) Wild type and rpa-9 nematodes were fed S. enterica on plates containing either 0.005 µg/mL actinomycin D or buffer. Wild type vs. Wild type+Act. D: p = 0.0261. (B) Wild type nematodes were grown on dsRNA for vector control or dsRNA for rps genes, and the number of living nematodes was scored after five days of feeding on S. enterica. Differences between vector and rps RNAi was statistically significant in all cases, p<0.0001. (C) Wild type and cep-1(gk138) nematodes were grown on dsRNA for vector control, dsRNA for nol-6, or dsRNA for rps genes, and the number of live versus dead animals was scored over time. Wild type vs. nol-6 RNAi: p<0.0001. Wild type vs. cep-1(gk138);nol-6 RNAi: p>0.05. Since cep-1(gk138) nematodes exhibit an Egl phenotype, the animals that die from matricide were censored. For each condition, 57–61 animals were used.

Mentions: C. elegans nol-6 encodes a nucleolar RNA associated protein (NRAP) that is conserved across eukaryotic organisms and involved in early stages of ribosome biogenesis [56]. The first step of generating a ribosome subunit requires the initial transcription of rDNA genes by RNA polymerase I (Pol-I). Inhibition of Pol-I by actinomycin D, an inhibitor of ribosome biogenesis [57],[58], leads to an enhanced resistance to S. enterica-mediated killing in wild-type nematodes without significantly affecting S. enterica virulence (Figure 5A). However, actinomycin D treatment in rpa-9 mutant nematodes has no effect (Figure 5A), suggesting that the ribosomal stress caused by the mutation cannot be further enhanced by drug treatment. Even though the nucleoli of S. enterica-infected animals are slightly larger than that of animals grown on E. coli and the nucleoli of rpa-9 mutants are also larger than the nucleoli of wild type nematodes when fed S. enterica (Figure S7), the small changes observed suggest that the overall structure of the nucleoli is not extensively affected.


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)

Nucleolar protein knockdown activates immunity against S. enterica in a p53/cep-1–dependent manner.(A) Wild type and rpa-9 nematodes were fed S. enterica on plates containing either 0.005 µg/mL actinomycin D or buffer. Wild type vs. Wild type+Act. D: p = 0.0261. (B) Wild type nematodes were grown on dsRNA for vector control or dsRNA for rps genes, and the number of living nematodes was scored after five days of feeding on S. enterica. Differences between vector and rps RNAi was statistically significant in all cases, p<0.0001. (C) Wild type and cep-1(gk138) nematodes were grown on dsRNA for vector control, dsRNA for nol-6, or dsRNA for rps genes, and the number of live versus dead animals was scored over time. Wild type vs. nol-6 RNAi: p<0.0001. Wild type vs. cep-1(gk138);nol-6 RNAi: p>0.05. Since cep-1(gk138) nematodes exhibit an Egl phenotype, the animals that die from matricide were censored. For each condition, 57–61 animals were used.
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC2734340&req=5

pgen-1000657-g005: Nucleolar protein knockdown activates immunity against S. enterica in a p53/cep-1–dependent manner.(A) Wild type and rpa-9 nematodes were fed S. enterica on plates containing either 0.005 µg/mL actinomycin D or buffer. Wild type vs. Wild type+Act. D: p = 0.0261. (B) Wild type nematodes were grown on dsRNA for vector control or dsRNA for rps genes, and the number of living nematodes was scored after five days of feeding on S. enterica. Differences between vector and rps RNAi was statistically significant in all cases, p<0.0001. (C) Wild type and cep-1(gk138) nematodes were grown on dsRNA for vector control, dsRNA for nol-6, or dsRNA for rps genes, and the number of live versus dead animals was scored over time. Wild type vs. nol-6 RNAi: p<0.0001. Wild type vs. cep-1(gk138);nol-6 RNAi: p>0.05. Since cep-1(gk138) nematodes exhibit an Egl phenotype, the animals that die from matricide were censored. For each condition, 57–61 animals were used.
Mentions: C. elegans nol-6 encodes a nucleolar RNA associated protein (NRAP) that is conserved across eukaryotic organisms and involved in early stages of ribosome biogenesis [56]. The first step of generating a ribosome subunit requires the initial transcription of rDNA genes by RNA polymerase I (Pol-I). Inhibition of Pol-I by actinomycin D, an inhibitor of ribosome biogenesis [57],[58], leads to an enhanced resistance to S. enterica-mediated killing in wild-type nematodes without significantly affecting S. enterica virulence (Figure 5A). However, actinomycin D treatment in rpa-9 mutant nematodes has no effect (Figure 5A), suggesting that the ribosomal stress caused by the mutation cannot be further enhanced by drug treatment. Even though the nucleoli of S. enterica-infected animals are slightly larger than that of animals grown on E. coli and the nucleoli of rpa-9 mutants are also larger than the nucleoli of wild type nematodes when fed S. enterica (Figure S7), the small changes observed suggest that the overall structure of the nucleoli is not extensively affected.

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