Stanford Advisors


All Publications

  • Nonproteolytic K29-Linked Ubiquitination of the PB2 Replication Protein of Influenza A Viruses by Proviral Cullin 4-Based E3 Ligases MBIO Karim, M., Biquand, E., Declercq, M., Jacob, Y., van der Werf, S., Demeret, C. 2020; 11 (2)


    The multifunctional nature of viral proteins is essentially driven by posttranslational modifications (PTMs) and is key for the successful outcome of infection. For influenza A viruses (IAVs), a composite pattern of PTMs regulates the activity of viral proteins. However, almost none are known that target the PB2 replication protein, except for inducing its degradation. We show here that PB2 undergoes a nonproteolytic ubiquitination during infection. We identified E3 ubiquitin ligases catalyzing this ubiquitination as two multicomponent RING-E3 ligases based on cullin 4 (CRL4s), which are both contributing to the levels of ubiquitinated forms of PB2 in infected cells. The CRL4 E3 ligase activity is required for the normal progression of the viral cycle and for maximal virion production, indicating that the CRL4s mediate a ubiquitin signaling that promotes infection. The CRL4s are recruiting PB2 through an unconventional bimodal interaction with both the DDB1 adaptor and DCAF substrate receptors. While able to bind to PB2 when engaged in the viral polymerase complex, the CRL4 factors do not alter transcription and replication of the viral segments during infection. CRL4 ligases catalyze different patterns of lysine ubiquitination on PB2. Recombinant viruses mutated in the targeted lysines showed attenuated viral production, suggesting that CRL4-mediated ubiquitination of PB2 contributes to IAV infection. We identified K29-linked ubiquitin chains as main components of the nonproteolytic PB2 ubiquitination mediated by the CRL4s, providing the first example of the role of this atypical ubiquitin linkage in the regulation of a viral infection.IMPORTANCE Successful infection by influenza A virus, a pathogen of major public health importance, involves fine regulation of the multiple functions of the viral proteins, which often relies on post-translational modifications (PTMs). The PB2 protein of influenza A viruses is essential for viral replication and a key determinant of host range. While PTMs of PB2 inducing its degradation have been identified, here we show that PB2 undergoes a regulating PTM signaling detected during infection, based on an atypical K29-linked ubiquitination and mediated by two multicomponent E3 ubiquitin ligases. Recombinant viruses impaired for CRL4-mediated ubiquitination are attenuated, indicating that ubiquitination of PB2 is necessary for an optimal influenza A virus infection. The CRL4 E3 ligases are required for normal viral cycle progression and for maximal virion production. Consequently, they represent potential candidate host factors for antiviral targets.

    View details for DOI 10.1128/mBio.00305-20

    View details for Web of Science ID 000531071300053

    View details for PubMedID 32265326

    View details for PubMedCentralID PMC7157767

  • Influenza A virus co-opts ERI1 exonuclease bound to histone mRNA to promote viral transcription Nucleic Acids Research Declercq, M., Biquand, E., Karim, M., Pietrosemoli, N., Jacob, Y., Demeret, C., Barbezange, C., Werf, S. v. 2020

    View details for DOI 10.1093/nar/gkaa771

  • Comparative Profiling of Ubiquitin Proteasome System Interplay with Influenza A Virus PB2 Polymerase Protein Recapitulating Virus Evolution in Humans MSPHERE Biquand, E., Poirson, J., Karim, M., Declercq, M., Malausse, N., Cassonnet, P., Barbezange, C., Straub, M., Jones, L., Munier, S., Naffakh, N., van der Werf, S., Jacob, Y., Masson, M., Demeret, C. 2017; 2 (6)
  • In silico analysis revealed Zika virus miRNAs associated with viral pathogenesis through alteration of host genes involved in immune response and neurological functions JOURNAL OF MEDICAL VIROLOGY Islam, M., Khan, M., Murad, M., Karim, M., Islam, A. 2019; 91 (9): 1584?94


    The concurrent Zika Virus (ZIKV) outbreaks in the United States and Northeast Brazil have evoked global surveillance. Zika infection has been correlated with severe clinical symptoms, such as microcephaly, Guillain-Barré syndrome, and other congenital brain abnormalities. Recent data suggest that ZIKV predominantly targets neural progenitor cells leading to neurological impairment. Despite the clinical evidence, detailed experimental mechanism of ZIKV neurotropic pathogenesis has not been fully understood yet. Here we hypothesized that ZIKV produces miRNAs, which target essential host genes involved in various cellular pathways facilitating their survival through immune evasion and progression of disease during brain development.From genome sequence information using several bioinformatic tools, we predicted pri-miRNAs, pre-miRNAs, and finally the mature miRNAs produced by ZIKV. We also identified their target genes and performed functional enrichment analysis to identify the biological processes associated with these genes. Finally, we analyzed a publicly available RNA-seq data set to determine the altered expression level of the targeted genes.From ZIKV genome sequence, we identified and validated 47 putative novel miRNAs. Functional enrichment of the targeted genes demonstrates the involvement of various biological pathways regulating cellular signaling, neurological functions, cancer, and fetal development. The expression analysis of these genes showed that ZIKV-produced miRNAs downregulate the key genes involved in these pathways, which in turn may lead to impaired brain development.Our finding proposes novel ZIKV miRNAs and their targets, which upon experimental validation could help developing new therapeutics to combat ZIKV infection and minimize ZIKV-mediated pathologies.

    View details for DOI 10.1002/jmv.25505

    View details for Web of Science ID 000481450500002

    View details for PubMedID 31095749

Footer Links:

Stanford Medicine Resources: