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RIG-I is required for the inhibition of measles virus by retinoids.

Soye KJ, Trottier C, Richardson CD, Ward BJ, Miller WH - PLoS ONE (2011)

Bottom Line: Vitamin A can significantly decrease measles-associated morbidity and mortality.Retinoid signaling was also found to act in combination with IFN to induce high levels of RIG-I expression.IRF-1 is known to be regulated by retinoids and MeV, but we found recruitment of IRF-1 to the RIG-I promoter by retinoids alone.

View Article: PubMed Central - PubMed

Affiliation: McGill University Health Center Research Institute, Department of Infectious Diseases, McGill University, Montreal, Quebec, Canada.

ABSTRACT
Vitamin A can significantly decrease measles-associated morbidity and mortality. Vitamin A can inhibit the replication of measles virus (MeV) in vitro through an RARα- and type I interferon (IFN)-dependent mechanism. Retinoid-induced gene I (RIG-I) expression is induced by retinoids, activated by MeV RNA and is important for IFN signaling. We hypothesized that RIG-I is central to retinoid-mediated inhibition of MeV in vitro. We demonstrate that RIG-I expression is increased in cells treated with retinoids and infected with MeV. The central role of RIG-I in the retinoid-anti-MeV effect was demonstrated in the Huh-7/7.5 model; the latter cells having non-functional RIG-I. RAR-dependent retinoid signaling was required for the induction of RIG-I by retinoids and MeV. Retinoid signaling was also found to act in combination with IFN to induce high levels of RIG-I expression. RIG-I promoter activation required both retinoids and MeV, as indicated by markers of active chromatin. IRF-1 is known to be regulated by retinoids and MeV, but we found recruitment of IRF-1 to the RIG-I promoter by retinoids alone. Using luciferase expression constructs, we further demonstrated that the IRF-1 response element of RIG-I was required for RIG-I activation by retinoids or IFN. These results reveal that retinoid treatment and MeV infection induces significant RIG-I. RIG-I is required for the retinoid-MeV antiviral response. The induction is dependent on IFN, retinoids and IRF-1.

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Retinoic acid nuclear receptors bind to the RIG-I promoter.(A) Diagram of the RIG-I promoter showing the known IRF1 binding site. Arrows represent the site of primers used in ChIP experiments. (B) RARα and RXR were immunoprecipitated from cells treated with 1 µM ATRA or DMSO (N = 2) (C) U937 cells were infected with MeV at an MOI of 0.1 and/or treated with 1 µM ATRA or DMSO for 24 hours. 1000 U/ml of IFNβ was used as a positive control. These samples were then immunoprecipitated RARα primary antibodies. The pulled-down DNA was analyzed by qPCR using primers specific for the RIG-I promoter as described in the materials and methods. Data presented are representative of three experiments performed in triplicate (N = 3). *p<0.05, **p<0.01, ***p<0.001.
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pone-0022323-g005: Retinoic acid nuclear receptors bind to the RIG-I promoter.(A) Diagram of the RIG-I promoter showing the known IRF1 binding site. Arrows represent the site of primers used in ChIP experiments. (B) RARα and RXR were immunoprecipitated from cells treated with 1 µM ATRA or DMSO (N = 2) (C) U937 cells were infected with MeV at an MOI of 0.1 and/or treated with 1 µM ATRA or DMSO for 24 hours. 1000 U/ml of IFNβ was used as a positive control. These samples were then immunoprecipitated RARα primary antibodies. The pulled-down DNA was analyzed by qPCR using primers specific for the RIG-I promoter as described in the materials and methods. Data presented are representative of three experiments performed in triplicate (N = 3). *p<0.05, **p<0.01, ***p<0.001.

Mentions: Fourteen putative retinoic acid response elements (RARE) were identified within 10000 bp of the RIG-I start site using Genomatix MatInspector software. Predicted RAREs were confirmed using the consensus sequences previously described [45]. For a DR5/DR2, the consensus sequence is: not C, G, G/T, not A, G/C, A, 2 or 5 nucleotides, A/G, G, G/T, G/T, C/A, A [45]. Using Chromatin Immunoprecipitation (ChIP) assays in our U937 model (Figure 5A), we found that both RARα and RXR bind to the RIG-I promoter (Figure 5B). Retinoid nuclear receptor binding to an RARE is not dependent on ligand binding [46]. RARα (Figure 5C) and RXR (data not shown) binding to the RIG-I promoter was not affected by treatment with either ATRA or IFNβ, or by MeV infection.


RIG-I is required for the inhibition of measles virus by retinoids.

Soye KJ, Trottier C, Richardson CD, Ward BJ, Miller WH - PLoS ONE (2011)

Retinoic acid nuclear receptors bind to the RIG-I promoter.(A) Diagram of the RIG-I promoter showing the known IRF1 binding site. Arrows represent the site of primers used in ChIP experiments. (B) RARα and RXR were immunoprecipitated from cells treated with 1 µM ATRA or DMSO (N = 2) (C) U937 cells were infected with MeV at an MOI of 0.1 and/or treated with 1 µM ATRA or DMSO for 24 hours. 1000 U/ml of IFNβ was used as a positive control. These samples were then immunoprecipitated RARα primary antibodies. The pulled-down DNA was analyzed by qPCR using primers specific for the RIG-I promoter as described in the materials and methods. Data presented are representative of three experiments performed in triplicate (N = 3). *p<0.05, **p<0.01, ***p<0.001.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3139622&req=5

pone-0022323-g005: Retinoic acid nuclear receptors bind to the RIG-I promoter.(A) Diagram of the RIG-I promoter showing the known IRF1 binding site. Arrows represent the site of primers used in ChIP experiments. (B) RARα and RXR were immunoprecipitated from cells treated with 1 µM ATRA or DMSO (N = 2) (C) U937 cells were infected with MeV at an MOI of 0.1 and/or treated with 1 µM ATRA or DMSO for 24 hours. 1000 U/ml of IFNβ was used as a positive control. These samples were then immunoprecipitated RARα primary antibodies. The pulled-down DNA was analyzed by qPCR using primers specific for the RIG-I promoter as described in the materials and methods. Data presented are representative of three experiments performed in triplicate (N = 3). *p<0.05, **p<0.01, ***p<0.001.
Mentions: Fourteen putative retinoic acid response elements (RARE) were identified within 10000 bp of the RIG-I start site using Genomatix MatInspector software. Predicted RAREs were confirmed using the consensus sequences previously described [45]. For a DR5/DR2, the consensus sequence is: not C, G, G/T, not A, G/C, A, 2 or 5 nucleotides, A/G, G, G/T, G/T, C/A, A [45]. Using Chromatin Immunoprecipitation (ChIP) assays in our U937 model (Figure 5A), we found that both RARα and RXR bind to the RIG-I promoter (Figure 5B). Retinoid nuclear receptor binding to an RARE is not dependent on ligand binding [46]. RARα (Figure 5C) and RXR (data not shown) binding to the RIG-I promoter was not affected by treatment with either ATRA or IFNβ, or by MeV infection.

Bottom Line: Vitamin A can significantly decrease measles-associated morbidity and mortality.Retinoid signaling was also found to act in combination with IFN to induce high levels of RIG-I expression.IRF-1 is known to be regulated by retinoids and MeV, but we found recruitment of IRF-1 to the RIG-I promoter by retinoids alone.

View Article: PubMed Central - PubMed

Affiliation: McGill University Health Center Research Institute, Department of Infectious Diseases, McGill University, Montreal, Quebec, Canada.

ABSTRACT
Vitamin A can significantly decrease measles-associated morbidity and mortality. Vitamin A can inhibit the replication of measles virus (MeV) in vitro through an RARα- and type I interferon (IFN)-dependent mechanism. Retinoid-induced gene I (RIG-I) expression is induced by retinoids, activated by MeV RNA and is important for IFN signaling. We hypothesized that RIG-I is central to retinoid-mediated inhibition of MeV in vitro. We demonstrate that RIG-I expression is increased in cells treated with retinoids and infected with MeV. The central role of RIG-I in the retinoid-anti-MeV effect was demonstrated in the Huh-7/7.5 model; the latter cells having non-functional RIG-I. RAR-dependent retinoid signaling was required for the induction of RIG-I by retinoids and MeV. Retinoid signaling was also found to act in combination with IFN to induce high levels of RIG-I expression. RIG-I promoter activation required both retinoids and MeV, as indicated by markers of active chromatin. IRF-1 is known to be regulated by retinoids and MeV, but we found recruitment of IRF-1 to the RIG-I promoter by retinoids alone. Using luciferase expression constructs, we further demonstrated that the IRF-1 response element of RIG-I was required for RIG-I activation by retinoids or IFN. These results reveal that retinoid treatment and MeV infection induces significant RIG-I. RIG-I is required for the retinoid-MeV antiviral response. The induction is dependent on IFN, retinoids and IRF-1.

Show MeSH
Related in: MedlinePlus