Interactome of the antiviral factor APOBEC3B during adenoviral infection

Résumé

Background. APOBEC3 (Apolipoprotein B mRNA Editing Catalytic Polypeptide-like, or A3) proteins are cytidine deaminases involved in viral restriction. A3s restrict viral replication through introduction of C-to-T mutations in the viral genome. Viruses have evolved to antagonize the A3s and counteract the innate immune response. Human adenoviruses (HAdVs) constitute a large family of DNA viruses. HAdVs cause mostly respiratory, gastrointestinal tract infections and conjunctivitis. Recently, our laboratory demonstrated that APOBEC3B (A3B), one of the seven members of the A3 family, acts as an adenoviral restrictor factor. We also proved that HAdVs antagonize A3B by reducing A3B protein level. Results. Our first objective was to determine whether the decrease in A3B protein levels during adenoviral infection is caused by a degradation mechanism. Preliminary experiments were conducted to test whether A3B is ubiquitinated during adenoviral infection and whether inhibition of the ubiquitin proteasome system (UPS) would prevent A3B degradation. In parallel, we performed a proximity-dependent biotinylation assay coupled to mass spectrometry (PDB-MS) to investigate the proxisome of A3B in mock-infected and HAdV infection contexts. Proteins identified were mainly associated with nuclear ribonucleoprotein complexes and cytosolic stress granules, suggesting that A3B occupies two distinct subcellular localizations. The adenoviral IVa2 protein, viral polymerase (Ad Pol) and several cellular RNA-binding proteins, including RBM47, ELAVL2 and AKAP8, were identified as potential A3B-interacting proteins and evaluated by co-immunoprecipitation (co-IP) assays. Conclusions and perspectives. The implication of an UPS in A3B protein level reduction during adenoviral infection requires further investigation, as results of the experiments led to inconclusive outcomes. The study of the interaction between A3B and Ad Pol, RBM47, ELAVL2 and AKAP8, did not yield definitive results. Complementary approaches are required to validate the interaction between A3B and IVa2. Three E3-Ubiquitin ligases were identified as potential A3B interactors. Further investigations will be necessary to validate the interactions and test the impact of these E3 ligases on A3B ubiquitination and half-life.

la date de réponse	20 janv. 2025
langue originale	Anglais
L'institution diplômante	Universite de Namur
Superviseur	Nicolas Gillet (Jury)