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Time-dependent recruitment of GAF, ISGF3 and IRF1 complexes to GAS, ISRE and composite genes shapes IFNa and IFNg activated transcriptional responses and explains functional overlap [CHIP-seq]

ABSTRACT: Although the core type I and type II IFN signaling pathways are distinct, their expression profiles show considerable overlap and are difficult to discern. Using a genome-wide RNAseq-ChIPseq integrative approach, our results identify a novel class of IFN-I and IFN-II responsive genes that use ISRE and GAS composite sites to recruit STAT1 and STAT2-containing ISGF3 and GAF-like complexes and IRF1 for optimal expression. Moreover, they support the existence of an analogous transcriptional regulatory mechanism of IFNα and IFNγ inducible genes, in which STAT1 and STAT2-containing ISGF3 and GAF-like complexes and IRF1 are recruited to individual or combined ISRE and GAS composite sites in an IFN- and time-dependent manner. In addition, we present proof for the involvement of an ISRE and GAS composite-dependent regulatory system in IFN-activated positive feedback regulation of the STAT1, STAT2, IRF9 and IRF1 genes and long-term response to IFNs, which depends on phosphorylation and expression of ISGF3, IRF1 and GAF-like components. These findings provide further insight in the existence of a novel intracellular amplifier circuit that offer an explanation for the existing molecular and functional overlap between IFN-I and IFN-II activated ISG expression.

ORGANISM(S): Homo sapiens

PROVIDER: GSE222667 | GEO | 2023/05/04

REPOSITORIES: GEO

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Project description:Type I Interferons (IFN-I) mediate cellular responses to virus infection. IFN-I induce IFN stimulated gene (ISG) expression by phosphorylating STAT1 and STAT2, and together with interferon regulatory factor (IRF)9, form the transcription complex ISGF3 that binds to the interferon-stimulated response element (ISRE) in ISG promoters. As a component of ISGF3 it is clear that STAT2 plays an essential role in the transcriptional responses to IFN-I with a strong dependence on STAT1. Previously, we showed that STAT2 also forms homodimers that interact with IRF9 (STAT2-IRF9) to activate transcription of ISRE containing ISGs in response to IFN-I. Indeed, evidence is accumulating for the existence of a STAT1-independent IFN-I signaling pathway, where STAT2-IRF9 can substitute the role of ISGF3. Here, we provide further insight in the transcriptional regulation and the biological implications of STAT2-IRF9 dependent IFN-I signaling. In human STAT1 KO cells overexpressing human STAT2 (U3C-STAT2) we observed that in response to IFN-I STAT2 homodimers interact with IRF9 to regulate ISG transcription. The IFN-I-induced phosphorylation profile of STAT2 in U3C-STAT2 was prolonged as compared to WT cells (2fTGH), which corresponded with the expression pattern of OAS2 that also depended on IRF9. Subsequent microarray analysis of IFN-I treated 2fTGH and U3C-STAT2 extended our initial observations and identified more than 60 known antiviral ISGs commonly up-regulated in both cell types. The expression profile of these ISGs was delayed and prolonged in U3C-STAT2 as opposed to the early and transient response in 2fTGH. Moreover, U3C-STAT2 were able to restore an antiviral response upon EMCV and VSV infection that was comparable to the response in 2fTGH. Together, our results strongly suggest that an alternative IFN-I-mediated, STAT2-IRF9 dependent signaling pathway exists that can generate an antiviral response without STAT1 and could be beneficial for example against viruses that directly block STAT1 and impair the formation of ISGF3.

Project description:Type I Interferons (IFN-I) mediate cellular responses to virus infection. IFN-I induces IFN-stimulated gene (ISG) expression by phosphorylating STAT1 and STAT2, and together with interferon regulatory factor (IRF9), form the transcription complex ISGF3 that binds to the interferon-stimulated response element (ISRE) in ISG promoters. As a component of ISGF3, it is clear that STAT2 plays an essential role in the transcriptional responses to IFN-I with a strong dependence on STAT1. Previously, we showed that STAT2 also forms homodimers that interact with IRF9 (STAT2-IRF9) to activate transcription of ISRE-containing ISGs in response to IFN-I. Indeed, evidence is accumulating for the existence of a STAT1-independent IFN-I signaling pathway, where STAT2-IRF9 can substitute the role of ISGF3. Here, we provide further insight in the transcriptional regulation and the biological implications of STAT2-IRF9 dependent IFN-I signaling. In human STAT1 KO cells overexpressing human STAT2 (U3C-STAT2), we observed that in response to IFN-I, STAT2 homodimers interact with IRF9 to regulate ISG transcription. The IFN-I-induced phosphorylation profile of STAT2 in U3C-STAT2 was prolonged as compared to WT cells (2fTGH), which corresponded with the expression pattern of OAS2 that also depended on IRF9. Subsequent microarray analysis of IFN-I treated 2fTGH and U3C-STAT2 extended our initial observations and identified more than 60 known antiviral ISGs commonly up-regulated in both cell types. The expression profile of these ISGs was delayed and prolonged in U3C-STAT2 as opposed to the early and transient response in 2fTGH. Moreover, U3C-STAT2 were able to restore an antiviral response upon EMCV and VSV infection that was comparable to the response in 2fTGH. Together, our results strongly suggest that an alternative IFN-I-mediated, STAT2-IRF9 dependent signaling pathway exists that can generate an antiviral response without STAT1 and could be beneficial for example against viruses that directly block STAT1 and impair the formation of ISGF3.

Project description:Atherosclerosis is a disease of large and medium-sized muscular arteries and is characterized by vascular inflammation and lipid-laden plaque formation within the intima of the vessel wall. Atherosclerosis is initiated by recruitment of blood leukocytes to the injured vascular endothelium and leads to altered contractility of Vascular Smooth Muscle Cells (VSMCs), acute and chronic luminal obstruction, abnormalities of blood flow and diminished oxygen supply to target organs. The pro-inflammatory pathways activated by Toll-like Receptors (TLRs), and Interferons (IFNs) have been identified as key components of atherogenesis. These pathways culminate in the activation of Signal Transducers and Activator of Transcription (STAT)1-containing complexes ISGF3 and GAF, and Nuclear factor-κB (NFκB) that coordinate expression of multiple chemokines, adhesion molecules, antiviral and antimicrobial proteins in vascular and immune cells. IFN-I and IFN-II participate in signaling cross-talk with TLR4 through combinatorial actions of ISGF3 and GAF with NF-kB leading to enhanced gene expression. Currently it is not clear how this signal integration is regulated at the genome-wide level and if similar mechanisms are activated by the different IFNs in vascular cells as compared to macrophages and dendritic cells. Therefore, we compared genome-wide transcriptional responses of mouse VSMCs, macrophages (BMDMs) and dendritic cells (DCs) in response to IFNα, IFNγ or LPS alone, or after combined treatment using RNA-seq. Consequently, commonly up-regulated genes in VSMCs, BMDMs and DCs could be identified after combined treatment with IFNα+LPS, as well as after combined treatment with IFNγ+LPS. Generally, in all three cell-types combined treatment with IFNα+LPS or IFNγ+LPS resulted in a synergistic increase in gene expression as compared to single treatments. Also, significant functional overlap could be observed between commonly upregulated genes in response to IFNα+LPS and IFNγ+LPS. Using ChIP-seq on chromatin from VSMCs, STAT1 and p65 bound IFNα+LPS and IFNγ+LPS up-regulated genes were identified, containing GAF/GAS, ISGF3/ISRE or NF-kB binding motifs located in promoter regions, but also to up- and downstream genomic regions. Comparing IFNα+LPS and IFNγ+LPS commonly upregulated genes identified a substantial overlap of ISRE-containing genes. Interestingly, STAT1 as part of ISGF3 was shown to bind the promoter of these ISRE-containing genes in response to IFNα as well as IFNγ. Moreover, different binding modes of STAT1-p65 co-binding were detected, including GAS-NFκB, ISRE-NFκB or GAS-ISRE-NFκB, shared by IFNα+LPS and IFNγ+LPS up-regulated genes. This cooperative involvement involved a STAT1-dependent role in the nearby recruitment of p65 already upon single IFNα or IFNγ treatment, via closely located GAS-NFĸB or ISRE-NFĸB binding sites in promoter regions. More important, this STAT1-p65 co-binding was significantly increased upon subsequent LPS exposure and resulted in amplified transcriptional activity of IFNα+LPS and IFNγ+LPS upregulated genes.

Dataset Information

Time-dependent recruitment of GAF, ISGF3 and IRF1 complexes to GAS, ISRE and composite genes shapes IFNa and IFNg activated transcriptional responses and explains functional overlap [CHIP-seq]

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