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Interferon regulatory factor 7 mediates obesity-associated MCP-1 transcription.

ABSTRACT: Hypertrophy, associated with adipocyte dysfunction, causes increased pro-inflammatory adipokine, and abnormal glucose and lipid metabolism, leading to insulin resistance and obesity-related-health problems. By combining DNA microarray and genomic data analyses to predict DNA binding motifs, we identified the transcription factor Interferon Regulatory Factor 7 (IRF7) as a possible regulator of genes related to adipocyte hypertrophy. To investigate the role of IRF7 in adipocytes, we examined gene expression patterns in 3T3-L1 cells infected with a retrovirus carrying the IRF7 gene and found that enforced IRF7 expression induced the expression of monocyte chemoattractant protein-1 (MCP-1), a key initial adipokine in the chronic inflammation of obesity. CRISPR/Cas9 mediated-suppression of IRF7 significantly reduced MCP-1 mRNA. Luciferase assays, chromatin immunoprecipitation PCR analysis and gel shift assay showed that IRF7 transactivates the MCP-1 gene by binding to its proximal Interferon Stimulation Response Element (ISRE), a putative IRF7 binding motif. IRF7 knockout mice exhibited lower expression of MCP-1 in epidydimal white adipose tissue under high-fat feeding conditions, suggesting the transcription factor is physiologically important for inducing MCP-1. Taken together, our results suggest that IRF7 transactivates MCP-1 mRNA in adipocytes, and it may be involved in the adipose tissue inflammation associated with obesity.

SUBMITTER: Kuroda M

PROVIDER: S-EPMC7241760 | biostudies-literature | 2020

REPOSITORIES: biostudies-literature

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Interferon regulatory factor 7 mediates obesity-associated MCP-1 transcription.

Kuroda Masashi M Nishiguchi Misa M Ugawa Naho N Ishikawa Etsuko E Kawabata Yasuyo Y Okamoto Saya S Sasaki Waka W Miyatake Yumiko Y Sebe Mayu M Masumoto Saeko S Tsutsumi Rie R Harada Nagakatsu N Sakaue Hiroshi H

PloS one 20200521 5

Hypertrophy, associated with adipocyte dysfunction, causes increased pro-inflammatory adipokine, and abnormal glucose and lipid metabolism, leading to insulin resistance and obesity-related-health problems. By combining DNA microarray and genomic data analyses to predict DNA binding motifs, we identified the transcription factor Interferon Regulatory Factor 7 (IRF7) as a possible regulator of genes related to adipocyte hypertrophy. To investigate the role of IRF7 in adipocytes, we examined gene ...[more]

PMID: 32437400

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Project description:Studies on "hit-and-run" effects by viral proteins are difficult when using traditional affinity precipitation-based techniques under dynamic conditions, because only proteins interacting at a specific instance in time can be precipitated by affinity purification. Recent advances in proximity labeling (PL) have enabled identification of both static and dynamic protein-protein interactions. In this study, we applied a PL method by generating recombinant Kaposi's sarcoma-associated herpesvirus (KSHV). KSHV, a gammaherpesvirus, uniquely encodes four interferon regulatory factors (IRF-1 to -4) that suppress host interferon responses, and we examined KSHV IRF-1 and IRF-4 neighbor proteins to identify cellular proteins involved in innate immune regulation. PL identified 213 and 70 proteins as neighboring proteins of viral IRF-1 (vIRF-1) and vIRF-4 during viral reactivation, and 47 proteins were shared between the two vIRFs; the list also includes three viral proteins, ORF17, thymidine kinase, and vIRF-4. Functional annotation of respective interacting proteins showed highly overlapping biological roles such as mRNA processing and transcriptional regulation by TP53. Innate immune regulation by these commonly interacting 44 cellular proteins was examined with small interfering RNAs (siRNAs), and the splicing factor 3B family proteins were found to be associated with interferon transcription and to act as suppressors of KSHV reactivation. We propose that recombinant mini-TurboID-KSHV is a powerful tool to probe key cellular proteins that play a role in KSHV replication and that selective splicing factors have a function in the regulation of innate immune responses.IMPORTANCE Viral protein interaction with a host protein shows at least two sides: (i) taking host protein functions for its own benefit and (ii) disruption of existing host protein complex formation to inhibit undesirable host responses. Due to the use of affinity precipitation approaches, the majority of studies have focused on how the virus takes advantage of the newly formed protein interactions for its own replication. Proximity labeling (PL), however, can also highlight transient and negative effects-those interactions which lead to dissociation from the existing protein complex. Here, we highlight the power of PL in combination with recombinant KSHV to study viral host interactions.

Project description:Transporter associated with antigen processing 2 (Tap-2) is responsible for ATP-dependent transport of peptides from the cytosol to the endoplasmic reticulum, where peptides bind to newly synthesized human leukocyte antigen (HLA) class I molecules, which are essential for cellular immune responses. Epstein-Barr virus (EBV) latent membrane protein 1 (LMP-1) has been shown to induce the expression of Tap-2. In this study, the induction of endogenous Tap-2 by LMP-1 is shown to be associated with and requires the expression of interferon regulatory factor 7 (IRF-7). In DG75 Burkitt's lymphoma (BL) cells, in which LMP-1 induces the expression of IRF-7, LMP-1 induced endogenous Tap-2, and ectopic expression of IRF-7 could enhance the induction. In Akata BL cells, in which LMP-1 could not induce IRF-7, LMP-1 could not induce Tap-2. Addition of IRF-7, which complements the defect in Akata cells, could stimulate the expression of Tap-2. Furthermore, LMP-1 and IRF-7A but not other IRF-7 splicing variants could activate endogenous Tap-2. A Tap-2 promoter reporter construct could be activated by the overexpression of IRF-7A. The activation could be specifically enhanced by LMP-1 and was dependent on an intact interferon-stimulated response element (ISRE) present in the Tap-2 promoter. Also, IRF-7 can bind to the Tap-2 promoter under physiological conditions in vivo, as shown by formaldehyde cross-linking, as well as to the Tap-2 ISRE in vitro, as shown by gel mobility shift assays. Furthermore, LMP-1 facilitates the phosphorylation and nuclear translocation of IRF-7. These data point to the role of IRF-7 as a secondary mediator of LMP-1-activated signal transduction for Tap-2 as follows: LMP-1 stimulates the expression of IRF-7 and facilitates its phosphorylation and nuclear translocation, and then the activated IRF-7 mediates the activation of the cellular Tap-2 gene. The induction of Tap-2 by IRF-7 and LMP-1 may have an important implication for the immune response to EBV and its persistence in vivo.

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Interferon regulatory factor 7 mediates obesity-associated MCP-1 transcription.

Publications

Interferon regulatory factor 7 mediates obesity-associated MCP-1 transcription.

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