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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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RIG-I expression required RAR signaling.(A) NB4 and R4 cells were infected with MeV at an MOI of 0.01, treated with 1 µM ATRA or DMSO and/or treated with 1000 U/mL IFNβ. After 48 hours, samples were harvested and analyzed for RIG-I expression and (B) RARβ expression by qPCR. Data presented are representative of two experiments performed in triplicate (N = 2). (C) U937 cells were infected at an MOI of 0.1 for 24 hours in the presence of 10 nM ATRA and/or 1000 nM of the RARα-selective antagonist RO 41-5253 (RO). Samples were analyzed for RIG-I expression by qPCR. Data presented are representative of three experiments performed in triplicate (N = 3). **p<0.01, ***p<0.001.
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pone-0022323-g004: RIG-I expression required RAR signaling.(A) NB4 and R4 cells were infected with MeV at an MOI of 0.01, treated with 1 µM ATRA or DMSO and/or treated with 1000 U/mL IFNβ. After 48 hours, samples were harvested and analyzed for RIG-I expression and (B) RARβ expression by qPCR. Data presented are representative of two experiments performed in triplicate (N = 2). (C) U937 cells were infected at an MOI of 0.1 for 24 hours in the presence of 10 nM ATRA and/or 1000 nM of the RARα-selective antagonist RO 41-5253 (RO). Samples were analyzed for RIG-I expression by qPCR. Data presented are representative of three experiments performed in triplicate (N = 3). **p<0.01, ***p<0.001.

Mentions: In NB4 cells, ATRA treatment alone had the ability to induce modest levels of RIG-I mRNA as measured by qPCR (Figure 4A) and western blot (data not shown). MeV infection of these cells by itself also induced moderate increases in RIG-I expression (Figure 4A, data not shown). Similar to the U937 cell model (Figure 1), the combination of ATRA treatment and MeV infection yielded a significant level of RIG-I mRNA (Figure 4A, data not shown). In R4 cells, resistance to retinoid signaling was first confirmed by demonstrating the inability of ATRA to induce the expression of RARβ, a well documented retinoid responsive gene (Figure 4B). In these cells, neither ATRA treatment alone, nor MeV infection alone, nor the combination could induce the expression of RIG-I mRNA (Figure 4A) or protein (data not shown). It is important to note that the antiviral effect of ATRA on MeV in NB4 cells is not due to retinoid induced cell differentiation as previously demonstrated by CD11b expression [8]. Increased apoptosis of NB4 cells is also not the cause of the antiviral effect as demonstrated in our previous work [8]. These observations demonstrate a requirement of RAR signaling for the induction of RIG-I.


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)

RIG-I expression required RAR signaling.(A) NB4 and R4 cells were infected with MeV at an MOI of 0.01, treated with 1 µM ATRA or DMSO and/or treated with 1000 U/mL IFNβ. After 48 hours, samples were harvested and analyzed for RIG-I expression and (B) RARβ expression by qPCR. Data presented are representative of two experiments performed in triplicate (N = 2). (C) U937 cells were infected at an MOI of 0.1 for 24 hours in the presence of 10 nM ATRA and/or 1000 nM of the RARα-selective antagonist RO 41-5253 (RO). Samples were analyzed for RIG-I expression by qPCR. Data presented are representative of three experiments performed in triplicate (N = 3). **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-g004: RIG-I expression required RAR signaling.(A) NB4 and R4 cells were infected with MeV at an MOI of 0.01, treated with 1 µM ATRA or DMSO and/or treated with 1000 U/mL IFNβ. After 48 hours, samples were harvested and analyzed for RIG-I expression and (B) RARβ expression by qPCR. Data presented are representative of two experiments performed in triplicate (N = 2). (C) U937 cells were infected at an MOI of 0.1 for 24 hours in the presence of 10 nM ATRA and/or 1000 nM of the RARα-selective antagonist RO 41-5253 (RO). Samples were analyzed for RIG-I expression by qPCR. Data presented are representative of three experiments performed in triplicate (N = 3). **p<0.01, ***p<0.001.
Mentions: In NB4 cells, ATRA treatment alone had the ability to induce modest levels of RIG-I mRNA as measured by qPCR (Figure 4A) and western blot (data not shown). MeV infection of these cells by itself also induced moderate increases in RIG-I expression (Figure 4A, data not shown). Similar to the U937 cell model (Figure 1), the combination of ATRA treatment and MeV infection yielded a significant level of RIG-I mRNA (Figure 4A, data not shown). In R4 cells, resistance to retinoid signaling was first confirmed by demonstrating the inability of ATRA to induce the expression of RARβ, a well documented retinoid responsive gene (Figure 4B). In these cells, neither ATRA treatment alone, nor MeV infection alone, nor the combination could induce the expression of RIG-I mRNA (Figure 4A) or protein (data not shown). It is important to note that the antiviral effect of ATRA on MeV in NB4 cells is not due to retinoid induced cell differentiation as previously demonstrated by CD11b expression [8]. Increased apoptosis of NB4 cells is also not the cause of the antiviral effect as demonstrated in our previous work [8]. These observations demonstrate a requirement of RAR signaling for the induction of RIG-I.

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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Related in: MedlinePlus