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Stubbe, M.

Role of E2A SUMOylation during productive infection with Human Adenovirus Type 5.

München, Technische Universität, Fakultät für Medizin, Diss., 2023, 191 S.
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Human Adenoviruses (HAdV) are non-enveloped viruses containing a linear, double- stranded DNA genome surrounded by an icosahedral capsid with type-specific antigens. HAdVs are often non-pathogenic for healthy individuals. However, in the absence of protective immunity, HAdV infections can become lethal as a result of uncontrolled immunopathology and processes, which are still far from being understood in detail. To ensure proper replication, DNA viruses express early viral genes to degrade or displace key regulators of cellular antiviral and immune response. In contrast, host-cells repress infection events through a network of transcriptional repressors and activators that typically regulate cellular homeostasis. The nuclear domains thought to be in charge for repressing viral DNA genomes are PML nuclear bodies (PML-NBs), interferon inducible, dot-like nuclear structures. Despite the fact that PML-NBs exhibit antiviral activity, many viruses including HAdVs position their genomes next to these structures via up to now unknown mechanism. PML-NBs represent the hotspots for host SUMO posttranslational modification. In HAdV infected cells these “SUMO factories” are located next to newly established replication centers indicated by the viral marker protein E2A. This work demonstrates that E2A represents a novel target of the host SUMOylation machinery, orchestrating essential E2A functions. Mimicking removal of SUMOylated E2A from the infected cell by generation of HAdV variants with mutations in the SUMO conjugation motif repressed viral replication properties. Furthermore, we observed that E2A SUMO PTM might impact HAdV gene splicing and packaging of the viral genome. The data shown here clearly illustrate the influence of E2A SUMOylation on PML-NBs subcellular localization. Biochemical analyses revealed that SUMO modified E2A interacts with PML and Sp100A. These interactions represent the so far unknown molecular bridge between HAdV replication centers and PML tracks, enabling the virus to utilize their transcription activating capacities. On the other hand, to prevent condensation of the viral chromatin, Sp100HMG being an epigenetic modulator and repressive factor for efficient HAdV infection is counteracted by active entrapment into HAdV replication centers on an E2A SUMOylation-dependent manner. HAdVs are classified as DNA tumor viruses due to their oncogenic capacity in non- permissive mammalian cells. They have developed intricate mechanisms to counteract host DNA damage response, including the activity of the cellular tumor suppressor p53. Several HAdV proteins are known to inhibit p53-mediated transcriptional activation, however even though it has been reported that temperature-sensitive mutations within E2A gene affect HAdV-mediated transformation, the connection between E2A and p53 has so far not been reported. Here, we identified E2A to be involved in the inhibition of p53-mediated transcription. E2A recruits p53 to HAdV replication centers during infection and to E2A containing domains in transfection settings. SUMOylated E2A promotes p53 degradation and E1B-55K interaction with PML-V that causes elevated p53 SUMOylation and subsequent inhibition of the transcription activating properties of the tumor suppressor. Additionally, functional E1B-55K prevents E2A binding to p53. In the absence of other viral factors E2A induces E1B-55K nuclear localization, reduces E1B-55K levels and SUMO PTM, thereby preventing E1B-55K-mediated p53 SUMOylation. Moreover, SUMOylated E2A interacts with Ubc9 and triggers the reduction of p53 SUMOylation, indicating the existence of an additional concept used by the virus to inhibit p53 activity using the HAdV DNA-binding protein E2A. Taken together, these data reveal a novel E2A SUMOylation based mechanism employed by HAdV to exploit beneficial cellular components and to simultaneously counteract the host antiviral and DNA damage response.
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Publication type Other: Thesis
Thesis type Doctoral thesis
Quellenangaben Volume: , Issue: , Pages: 191 S. Article Number: , Supplement: ,
University Technische Universität
University place München
Faculty Fakultät für Medizin
Institute(s) Institute of Virology (VIRO)