1
|
Schwanke H, Gonçalves Magalhães V, Schmelz S, Wyler E, Hennig T, Günther T, Grundhoff A, Dölken L, Landthaler M, van Ham M, Jänsch L, Büssow K, van den Heuvel J, Blankenfeldt W, Friedel CC, Erhard F, Brinkmann MM. The Cytomegalovirus M35 Protein Directly Binds to the Interferon-β Enhancer and Modulates Transcription of Ifnb1 and Other IRF3-Driven Genes. J Virol 2023; 97:e0040023. [PMID: 37289084 PMCID: PMC10308904 DOI: 10.1128/jvi.00400-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2023] [Accepted: 05/04/2023] [Indexed: 06/09/2023] Open
Abstract
Induction of type I interferon (IFN) gene expression is among the first lines of cellular defense a virus encounters during primary infection. We previously identified the tegument protein M35 of murine cytomegalovirus (MCMV) as an essential antagonist of this antiviral system, showing that M35 interferes with type I IFN induction downstream of pattern-recognition receptor (PRR) activation. Here, we report structural and mechanistic details of M35's function. Determination of M35's crystal structure combined with reverse genetics revealed that homodimerization is a key feature for M35's immunomodulatory activity. In electrophoretic mobility shift assays (EMSAs), purified M35 protein specifically bound to the regulatory DNA element that governs transcription of the first type I IFN gene induced in nonimmune cells, Ifnb1. DNA-binding sites of M35 overlapped with the recognition elements of interferon regulatory factor 3 (IRF3), a key transcription factor activated by PRR signaling. Chromatin immunoprecipitation (ChIP) showed reduced binding of IRF3 to the host Ifnb1 promoter in the presence of M35. We furthermore defined the IRF3-dependent and the type I IFN signaling-responsive genes in murine fibroblasts by RNA sequencing of metabolically labeled transcripts (SLAM-seq) and assessed M35's global effect on gene expression. Stable expression of M35 broadly influenced the transcriptome in untreated cells and specifically downregulated basal expression of IRF3-dependent genes. During MCMV infection, M35 impaired expression of IRF3-responsive genes aside of Ifnb1. Our results suggest that M35-DNA binding directly antagonizes gene induction mediated by IRF3 and impairs the antiviral response more broadly than formerly recognized. IMPORTANCE Replication of the ubiquitous human cytomegalovirus (HCMV) in healthy individuals mostly goes unnoticed but can impair fetal development or cause life-threatening symptoms in immunosuppressed or -deficient patients. Like other herpesviruses, CMV extensively manipulates its hosts and establishes lifelong latent infections. Murine CMV (MCMV) presents an important model system as it allows the study of CMV infection in the host organism. We previously showed that during entry into host cells, MCMV virions release the evolutionary conserved protein M35 protein to immediately dampen the antiviral type I interferon (IFN) response induced by pathogen detection. Here, we show that M35 dimers bind to regulatory DNA elements and interfere with recruitment of interferon regulatory factor 3 (IRF3), a key cellular factor for antiviral gene expression. Thereby, M35 interferes with expression of type I IFNs and other IRF3-dependent genes, reflecting the importance for herpesviruses to avoid IRF3-mediated gene induction.
Collapse
Affiliation(s)
- Hella Schwanke
- Institute of Genetics, Technische Universität Braunschweig, Braunschweig, Germany
- Virology and Innate Immunity Research Group, Helmholtz Centre for Infection Research, Braunschweig, Germany
| | | | - Stefan Schmelz
- Department Structure and Function of Proteins, Helmholtz Centre for Infection Research, Braunschweig, Germany
| | - Emanuel Wyler
- Berlin Institute for Medical Systems Biology, Max Delbrück Center for Molecular Medicine, Helmholtz Association, Berlin, Germany
| | - Thomas Hennig
- Institute for Virology and Immunobiology, Julius-Maximilians-Universität Würzburg, Würzburg, Germany
| | | | | | - Lars Dölken
- Institute for Virology and Immunobiology, Julius-Maximilians-Universität Würzburg, Würzburg, Germany
| | - Markus Landthaler
- Berlin Institute for Medical Systems Biology, Max Delbrück Center for Molecular Medicine, Helmholtz Association, Berlin, Germany
- Institute for Biology, Humboldt-Universität zu Berlin, Berlin, Germany
| | - Marco van Ham
- Cellular Proteome Research Group, Helmholtz Centre for Infection Research, Braunschweig, Germany
| | - Lothar Jänsch
- Cellular Proteome Research Group, Helmholtz Centre for Infection Research, Braunschweig, Germany
- Institute for Microbiology, Technische Universität Braunschweig, Braunschweig, Germany
| | - Konrad Büssow
- Department Structure and Function of Proteins, Helmholtz Centre for Infection Research, Braunschweig, Germany
| | - Joop van den Heuvel
- Department Structure and Function of Proteins, Helmholtz Centre for Infection Research, Braunschweig, Germany
| | - Wulf Blankenfeldt
- Department Structure and Function of Proteins, Helmholtz Centre for Infection Research, Braunschweig, Germany
- Institute for Biochemistry, Biotechnology and Bioinformatics, Technische Universität Braunschweig, Braunschweig, Germany
| | - Caroline C. Friedel
- Institute of Informatics, Ludwig-Maximilians-Universität München, Munich, Germany
| | - Florian Erhard
- Institute for Virology and Immunobiology, Julius-Maximilians-Universität Würzburg, Würzburg, Germany
| | - Melanie M. Brinkmann
- Institute of Genetics, Technische Universität Braunschweig, Braunschweig, Germany
- Virology and Innate Immunity Research Group, Helmholtz Centre for Infection Research, Braunschweig, Germany
| |
Collapse
|