Interference of the viral effector proteins pp71 and IE1 with intrinsic and innate immunity against human cytomegalovirus infections
Final Report Abstract
PML-NBs (nuclear bodies) are subnuclear structures that can be defined as SUMOylation-dependent accumulations of a large number (>140) of cellular proteins. The promyelocytic leukemia protein PML acts as an essential scaffold for these accumulations. The autoantigen Sp100 and the chromatinmodifiers Daxx and ATRX are additional important components. We were able to demonstrate that PML-NBs inhibit viral infections by acting as a cell-intrinsic barrier. Furthermore, we detected coactivation of the interferon-response by PML-NBs. However, during infection with human cytomegalovirus (HCMV) the viral effector proteins pp71 and IE1 counteract these antiviral functions. During this project we were able to solve the crystal structures of the IE1 proteins of human and rat cytomegalovirus. Despite limited amino acid sequence identity of 9% the proteins share a highly conserved fold structure with species-specific adaptations. In addition to species-specific binding of IE1 to PML proteins, we identified the protein FEN-1 (FLAP endonuclease 1) as a novel cellular interaction partner. A further characterization of this interaction revealed a novel mechanism how a viral regulatory protein activates FEN-1 in order to overcome replication barriers. Furthermore, this project revealed that PML-NBs are not only able to entrap and inactivate viral nucleic acids in a reversible manner, but we observed that this is also true for viral proteins (e.g. viral capsids). This could be demonstrated by ultrastructural characterization of giant PML-NBs that form after infection of cells with HCMV exhibiting a deletion of ie1. Finally, we were able to further clarify how IE1 and pp71 are able to inhibit the native immune response: IE1 induces the citrullination of interferonregulated proteins resulting in abrogation of their antiviral function. The PML-NB component ATRX was identified as a broadly acting coactivator of native immune responses which modulates the chromatin structure of distinct interferon-stimulated genes upon IFN treatment. Consequently, mutations in ATRX that are frequently found in human tumors and viral effector proteins that target ATRX are both able to compromise the native immune response.
Publications
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A Virally Encoded DeSUMOylase Activity Is Required for Cytomegalovirus Reactivation from Latency. Cell Reports, 24(3), 594-606.
Poole, Emma L.; Kew, Verity G.; Lau, Jonathan C.H.; Murray, Matthew J.; Stamminger, Thomas; Sinclair, John H. & Reeves, Matthew B.
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Centrosomal protein TRIM43 restricts herpesvirus infection by regulating nuclear lamina integrity. Nature Microbiology, 4(1), 164-176.
Full, Florian; van Gent, Michiel; Sparrer, Konstantin M. J.; Chiang, Cindy; Zurenski, Matthew A.; Scherer, Myriam; Brockmeyer, Norbert H.; Heinzerling, Lucie; Stürzl, Michael; Korn, Klaus; Stamminger, Thomas; Ensser, Armin & Gack, Michaela U.
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Chromatin-Remodeling Factor SPOC1 Acts as a Cellular Restriction Factor against Human Cytomegalovirus by Repressing the Major Immediate Early Promoter. Journal of Virology, 92(14).
Reichel, Anna; Stilp, Anne-Charlotte; Scherer, Myriam; Reuter, Nina; Lukassen, Sören; Kasmapour, Bahram; Schreiner, Sabrina; Cicin-Sain, Luka; Winterpacht, Andreas & Stamminger, Thomas
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A Noncanonical Function of Polycomb Repressive Complexes Promotes Human Cytomegalovirus Lytic DNA Replication and Serves as a Novel Cellular Target for Antiviral Intervention. Journal of Virology, 93(9).
Svrlanska, Adriana; Reichel, Anna; Schilling, Eva-Maria; Scherer, Myriam; Stamminger, Thomas & Reuter, Nina
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Cytomegalovirus immediate-early 1 proteins form a structurally distinct protein class with adaptations determining cross-species barriers. PLOS Pathogens, 17(8), e1009863.
Schweininger, Johannes; Scherer, Myriam; Rothemund, Franziska; Schilling, Eva-Maria; Wörz, Sonja; Stamminger, Thomas & Muller, Yves A.
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Functional regulation of the structure-specific endonuclease FEN1 by the human cytomegalovirus protein IE1 suggests a role for the re-initiation of stalled viral replication forks. PLOS Pathogens, 17(3), e1009460.
Schilling, Eva-Maria; Scherer, Myriam; Rothemund, Franziska & Stamminger, Thomas
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Author response: Dual signaling via interferon and DNA damage response elicits entrapment by giant PML nuclear bodies. eLife Sciences Publications, Ltd.
Scherer, Myriam; Read, Clarissa; Neusser, Gregor; Kranz, Christine; Kuderna, Anna K.; Müller, Regina; Full, Florian; Wörz, Sonja; Reichel, Anna; Schilling, Eva-Maria; Walther, Paul & Stamminger, Thomas
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The chromatin remodeling protein ATRX positively regulates IRF3-dependent type I interferon production and interferon-induced gene expression. PLOS Pathogens, 18(8), e1010748.
Stilp, Anne-Charlotte; Scherer, Myriam; König, Patrick; Fürstberger, Axel; Kestler, Hans A. & Stamminger, Thomas
