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Phosphorylation of STAT2 on serine-734 negatively regulates the IFN-?-induced antiviral response.

ABSTRACT: Serine phosphorylation of STAT proteins is an important post-translational modification event that, in addition to tyrosine phosphorylation, is required for strong transcriptional activity. However, we recently showed that phosphorylation of STAT2 on S287 induced by type I interferons (IFN-? and IFN-?), evoked the opposite effect. S287-STAT2 phosphorylation inhibited the biological effects of IFN-?. We now report the identification and characterization of S734 on the C-terminal transactivation domain of STAT2 as a new phosphorylation site that can be induced by type I IFNs. IFN-?-induced S734-STAT2 phosphorylation displayed different kinetics to that of tyrosine phosphorylation. S734-STAT2 phosphorylation was dependent on STAT2 tyrosine phosphorylation and JAK1 kinase activity. Mutation of S734-STAT2 to alanine (S734A) enhanced IFN-?-driven antiviral responses compared to those driven by wild-type STAT2. Furthermore, DNA microarray analysis demonstrated that a small subset of type I IFN stimulated genes (ISGs) was induced more by IFN? in cells expressing S734A-STAT2 when compared to wild-type STAT2. Taken together, these studies identify phosphorylation of S734-STAT2 as a new regulatory mechanism that negatively controls the type I IFN-antiviral response by limiting the expression of a select subset of antiviral ISGs.

SUBMITTER: Steen HC

PROVIDER: S-EPMC6518330 | biostudies-literature | 2016 Nov

REPOSITORIES: biostudies-literature

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Phosphorylation of STAT2 on serine-734 negatively regulates the IFN-α-induced antiviral response.

Steen Håkan C HC Kotredes Kevin P KP Nogusa Shoko S Harris Michele Y MY Balachandran Siddharth S Gamero Ana M AM

Journal of cell science 20161019 22

Serine phosphorylation of STAT proteins is an important post-translational modification event that, in addition to tyrosine phosphorylation, is required for strong transcriptional activity. However, we recently showed that phosphorylation of STAT2 on S287 induced by type I interferons (IFN-α and IFN-β), evoked the opposite effect. S287-STAT2 phosphorylation inhibited the biological effects of IFN-α. We now report the identification and characterization of S734 on the C-terminal transactivation d ...[more]

PMID: 27802159

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Project description:The phosphatase Cdc25A plays an important role in cell cycle regulation by dephosphorylating its substrates, such as cyclin-dependent kinases. In this study, we demonstrate that Cdc25A negatively regulates RIG-I-mediated antiviral signaling. We found that ectopic expression of Cdc25A in 293T cells inhibits the activation of beta interferon (IFN-?) induced by Sendai virus and poly(I·C), while knockdown of Cdc25A enhances the transcription of IFN-? stimulated by RNA virus infection. The inhibitory effect of Cdc25A on the antiviral immune response is mainly dependent on its phosphatase activity. Data from a luciferase assay indicated that Cdc25A can inhibit TBK1-mediated activation of IFN-?. Further analysis indicated that Cdc25A can interact with TBK1 and reduce the phosphorylation of TBK1 at S172, which in turn decreases the phosphorylation of its downstream substrate IRF3. Consistently, knockdown of Cdc25A upregulates the phosphorylation of both TBK1-S172 and IRF3 in Sendai virus-infected or TBK1-transfected 293T cells. In addition, we confirmed that Cdc25A can directly dephosphorylate TBK1-S172-p. These results demonstrate that Cdc25A inhibits the antiviral immune response by reducing the active form of TBK1. Using herpes simplex virus 1 (HSV-1) infection, an IFN-? reporter assay, and reverse transcription-quantitative PCR (RT-qPCR), we demonstrated that Cdc25A can also inhibit DNA virus-induced activation of IFN-?. Using a vesicular stomatitis virus (VSV) infection assay, we confirmed that Cdc25A can repress the RIG-I-like receptor (RLR)-mediated antiviral immune response and influence the antiviral status of cells. In conclusion, we demonstrate that Cdc25A negatively regulates the antiviral immune response by inhibiting TBK1 activity.IMPORTANCE The RLR-mediated antiviral immune response is critical for host defense against RNA virus infection. However, the detailed mechanism for balancing the RLR signaling pathway in host cells is not well understood. We found that the phosphatase Cdc25A negatively regulates the RNA virus-induced innate immune response. Our studies indicate that Cdc25A inhibits the RLR signaling pathway via its phosphatase activity. We demonstrated that Cdc25A reduces TBK1 activity and consequently restrains the activation of IFN-? transcription as well as the antiviral status of nearby cells. We showed that Cdc25A can also inhibit DNA virus-induced activation of IFN-?. Taken together, our findings uncover a novel function and mechanism for Cdc25A in regulating antiviral immune signaling. These findings reveal Cdc25A as an important negative regulator of antiviral immunity and demonstrate its role in maintaining host cell homeostasis following viral infection.

Dataset Information

Phosphorylation of STAT2 on serine-734 negatively regulates the IFN-?-induced antiviral response.

Publications

Phosphorylation of STAT2 on serine-734 negatively regulates the IFN-α-induced antiviral response.

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