Regulation of the RP-MDM2-P53 pathway by SUMO

The ribosomal protein L11 integrate different types of stress into a p53-mediated response. Here we analyzed the impact of the ubiquitin-like protein SUMO on the RPL11-MDM2-p53 signaling. We show that SUMO modify RPL11, mutation of all lysine residues in RPL11 did not abolish SUMOylation, suggesting that this conjugation occurs through an alternative non-canonical SUMOylation pathway. We find that SUMO downregulates the conjugation of the ubiquitin-like protein NEDD8 to RPL11 and promotes the translocation of RPL11 outside of the nucleoli. Moreover, the SUMO conjugating enzyme, Ubc9, is required for RPL11-mediated activation of p53. SUMOylation of RPL11 is triggered by ribosomal stress as well as by ARF. The ribosomal protein L23 and ARF can be also modulated by SUMO. In addition, this study has led us to advance in the knowledge of post-translational modifications by ubiquitin-like proteins demonstrating that SUMO can bind to a substrate in lysine independent manner and that there is an interplay between SUMOylation and NEDDylation

The Interaction of Viruses with the Cellular Senescence Response

Cellular senescence is viewed as a mechanism to prevent malignant transformation, but when it is chronic, as occurs in age-related diseases, it may have adverse effects on cancer. Therefore, targeting senescent cells is a novel therapeutic strategy against senescence-associated diseases. In addition to its role in cancer protection, cellular senescence is also considered a mechanism to control virus replication. Both interferon treatment and some viral infections can trigger cellular senescence as a way to restrict virus replication. However, activation of the cellular senescence program is linked to the alteration of different pathways, which can be exploited by some viruses to improve their replication. It is, therefore, important to understand the potential impact of senolytic agents on viral propagation. Here we focus on the relationship between virus and cellular senescence and the reported effects of senolytic compounds on virus replicationThis research was funded by Ministry of Science, Innovation and Universities and FEDER (BFU-2017-88880-P) and Xunta de Galicia (ED431G 2019/02). RS and SV are predoctoral fellows funded by Xunta de Galicia-Consellería de Cultura, Educación y Ordenación Universitaria (ED481A-2020/160 and ED481A-2018/110, respectively)S

Cell senescence is an antiviral defense mechanism

Cellular senescence is often considered a protection mechanism triggered by conditions that impose cellular stress. Continuous proliferation, DNA damaging agents or activated oncogenes are well-known activators of cell senescence. Apart from a characteristic stable cell cycle arrest, this response also involves a proinflammatory phenotype known as senescence-associated secretory phenotype (SASP). This, together with the widely known interference with senescence pathways by some oncoviruses, had led to the hypothesis that senescence may also be part of the host cell response to fight virus. Here, we evaluate this hypothesis using vesicular stomatitis virus (VSV) as a model. Our results show that VSV replication is significantly impaired in both primary and tumor senescent cells in comparison with non-senescent cells, and independently of the stimulus used to trigger senescence. Importantly, we also demonstrate a protective effect of senescence against VSV in vivo. Finally, our results identify the SASP as the major contributor to the antiviral defense exerted by cell senescence in vitro, and points to a role activating and recruiting the immune system to clear out the infection. Thus, our study indicates that cell senescence has also a role as a natural antiviral defense mechanism.This work was supported by Grant BFU2014- 58530-P from the Ministry of Economy and Competitiveness of Spain and EU-FEDER. MC is a Miguel Servet investigator supported by an ISCIII and EU-FEDER grant (PI14/00554). AEM is a recipient of a FPI predoctoral fellowship from the Ministry of Economy and Competitiveness of Spain. We are grateful to Dr. I Ventoso for providing the anti-VSV-G antibody.Peer reviewe

Regulation of Ebola virus VP40 matrix protein by SUMO

The matrix protein of Ebola virus (EBOV) VP40 regulates viral budding, nucleocapsid recruitment, virus structure and stability, viral genome replication and transcription, and has an intrinsic ability to form virus-like particles. The elucidation of the regulation of VP40 functions is essential to identify mechanisms to inhibit viral replication and spread. Post-translational modifications of proteins with ubiquitin-like family members are common mechanisms for the regulation of host and virus multifunctional proteins. Thus far, no SUMOylation of VP40 has been described. Here we demonstrate that VP40 is modified by SUMO and that SUMO is included into the viral like particles (VLPs). We demonstrate that lysine residue 326 in VP40 is involved in SUMOylation, and by analyzing a mutant in this residue we show that SUMO conjugation regulates the stability of VP40 and the incorporation of SUMO into the VLPs. Our study indicates for the first time, to the best of our knowledge, that EBOV hijacks the cellular SUMOylation system in order to modify its own proteins. Modulation of the VP40-SUMO interaction may represent a novel target for the therapy of Ebola virus infectionWe thank Sergio Gomez-Medina for excellent technical assistance. Funding at the laboratory of CR is provided by BFU-2014-58530. Work at the laboratory of CSM is supported by BFU2013-41249-P. This work was partially funded by the Lebniz Association (Prämie ERC Starting Grant 2013 to CM-F). The Heinrich-Pette-Institute is financed by the German Federal Ministry of Health and the Freie und Hansestadt Hamburg. AEM is supported by the Spanish Ministry of Economy and Competitiveness (FPI Fellowship). CFC-H is supported by CONACYT. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscriptS

Interplay between SUMOylation and NEDDylation regulates RPL11 localization and function

The ribosomal protein L11 (RPL11) integrates different types of stress into a p53‐mediated response. Here, we analyzed the impact of the ubiquitin‐like protein SUMO on the RPL11‐mouse double‐minute 2 homolog‐p53 signaling. We show that small ubiquitin‐related modifier (SUMO)1 and SUMO2 covalently modify RPL11. We find that SUMO negatively modulates the conjugation of the ubiquitin‐like protein neural precursor cell‐expressed developmentally downregulated 8 (NEDD8) to RPL11 and promotes the translocation of the RP outside of the nucleoli. Moreover, the SUMO‐conjugating enzyme, Ubc9, is required for RPL11‐mediated activation of p53. SUMOylation of RPL11 is triggered by ribosomal stress, as well as by alternate reading frame protein upregulation. Collectively, our data identify SUMO protein conjugation to RPL11 as a new regulator of the p53‐mediated cellular response to different types of stress and reveal a previously unknown SUMO‐NEDD8 interplay

Expression of the Ebola Virus VP24 Protein Compromises the Integrity of the Nuclear Envelope and Induces a Laminopathy- Like Cellular Phenotype

ABSTRACT Ebola virus (EBOV) VP24 protein is a nucleocapsid-associated protein that inhibits interferon (IFN) gene expression and counteracts the IFN-mediated antiviral response, preventing nuclear import of signal transducer and activator of transcription 1 (STAT1). Proteomic studies to identify additional EBOV VP24 partners have pointed to the nuclear membrane component emerin as a potential element of the VP24 cellular interactome. Here, we have further studied this interaction and its impact on cell biology. We demonstrate that VP24 interacts with emerin but also with other components of the inner nuclear membrane, such as lamin A/C and lamin B. We also show that VP24 diminishes the interaction between emerin and lamin A/C and compromises the integrity of the nuclear membrane. This disruption is associated with nuclear morphological abnormalities, activation of a DNA damage response, the phosphorylation of extracellular signal-regulated kinase (ERK), and the induction of interferon-stimulated gene 15 (ISG15). Interestingly, expression of VP24 also promoted the cytoplasmic translocation and downmodulation of barrier-to-autointegration factor (BAF), a common interactor of lamin A/C and emerin, leading to repression of the BAF-regulated CSF1 gene. Importantly, we found that EBOV infection results in the activation of pathways associated with nuclear envelope damage, consistent with our observations in cells expressing VP24. In summary, here we demonstrate that VP24 acts at the nuclear membrane, causing morphological and functional changes in cells that recapitulate several of the hallmarks of laminopathy diseases. IMPORTANCE The Ebola virus (EBOV) VP24 protein is a nucleocapsid-associated protein with multiple functions. Proteomic studies have identified the cellular nuclear membrane component emerin as a potential VP24 interactor. Here, we demonstrate that VP24 not only interacts with emerin but also with lamin A/C and lamin B, prompting nuclear membrane disruption. This disruption is associated with nuclear morphological abnormalities, activation of a DNA damage response, the phosphorylation of extracellular signal-regulated kinase (ERK), and the induction of interferon-stimulated gene 15 (ISG15). Interestingly, VP24 also promotes the cytoplasmic translocation and downmodulation of barrier-to-autointegration factor (BAF), leading to repression of the BAF-regulated CSF1 gene. Finally, we show that EBOV infection also results in the activation of pathways associated with nuclear envelope damage, consistent with our observations in cells expressing VP24. These results reveal novel activities of EBOV VP24 protein, resulting in a cell phenotype similar to that of most laminopathies, with potential impact on EBOV replication

eIF5A is activated by virus infection or dsRNA and facilitates virus replication through modulation of interferon production

Active hypusine-modified initiation elongation factor 5A is critical for cell proliferation and differentiation, embryonic development, and innate immune response of macrophages to bacterial infection. Here, we demonstrate that both virus infection and double-stranded RNA viral mimic stimulation induce the hypusination of eIF5A. Furthermore, we show that activation of eIF5A is essential for the replication of several RNA viruses including influenza A virus, vesicular stomatitis virus, chikungunya virus, mayaro virus, una virus, zika virus, and punta toro virus. Finally, our data reveal that inhibition of eIF5A hypusination using the spermidine analog GC7 or siRNA-mediated downmodulation of eIF5A1 induce upregulation of endoplasmic reticulum stress marker proteins and trigger the transcriptional induction of interferon and interferon-stimulated genes, mechanisms that may explain the broad-spectrum antiviral activity of eIF5A inhibition

The Interaction of Viruses with the Cellular Senescence Response

© 2020 by the authors.Cellular senescence is viewed as a mechanism to prevent malignant transformation, but when it is chronic, as occurs in age-related diseases, it may have adverse effects on cancer. Therefore, targeting senescent cells is a novel therapeutic strategy against senescence-associated diseases. In addition to its role in cancer protection, cellular senescence is also considered a mechanism to control virus replication. Both interferon treatment and some viral infections can trigger cellular senescence as a way to restrict virus replication. However, activation of the cellular senescence program is linked to the alteration of different pathways, which can be exploited by some viruses to improve their replication. It is, therefore, important to understand the potential impact of senolytic agents on viral propagation. Here we focus on the relationship between virus and cellular senescence and the reported effects of senolytic compounds on virus replication.This research was funded by Ministry of Science, Innovation and Universities and FEDER (BFU-2017-88880-P) and Xunta de Galicia (ED431G 2019/02). RS and SV are predoctoral fellows funded by Xunta de Galicia-Consellería de Cultura, Educación y Ordenación Universitaria (ED481A-2020/160 and ED481A-2018/110, respectively)

Cell senescence is an antiviral defense mechanism

Cellular senescence is often considered a protection mechanism triggered by conditions that impose cellular stress. Continuous proliferation, DNA damaging agents or activated oncogenes are well-known activators of cell senescence. Apart from a characteristic stable cell cycle arrest, this response also involves a proinflammatory phenotype known as senescence-associated secretory phenotype (SASP). This, together with the widely known interference with senescence pathways by some oncoviruses, had led to the hypothesis that senescence may also be part of the host cell response to fight virus. Here, we evaluate this hypothesis using vesicular stomatitis virus (VSV) as a model. Our results show that VSV replication is significantly impaired in both primary and tumor senescent cells in comparison with non-senescent cells, and independently of the stimulus used to trigger senescence. Importantly, we also demonstrate a protective effect of senescence against VSV in vivo. Finally, our results identify the SASP as the major contributor to the antiviral defense exerted by cell senescence in vitro, and points to a role activating and recruiting the immune system to clear out the infection. Thus, our study indicates that cell senescence has also a role as a natural antiviral defense mechanism.This work was supported by Grant BFU2014- 58530-P from the Ministry of Economy and Competitiveness of Spain and EU-FEDER. MC is a Miguel Servet investigator supported by an ISCIII and EU-FEDER grant (PI14/00554). AEM is a recipient of a FPI predoctoral fellowship from the Ministry of Economy and Competitiveness of SpainS