Antagonization of the APOBEC3B antiviral factor by Adenoviruses

Résumé

Background: APOBEC3 (Apolipoprotein B mRNA Editing enzyme, Catalytic polypeptide-like 3) proteins are cytidine deaminases turning cytosine into uracil. The APOBEC3s are innate antiviral effectors restricting viral replication through viral genome deamination. Human adenoviruses constitute a large family of DNA viruses causing generally mild respiratory, gastrointestinal, or ocular infections. Also, genetically modified adenoviruses are used as vaccines or oncolytic viruses. We recently demonstrated that APOBEC3B (A3B), one of the seven members of the APOBEC3 family, restricts adenoviral replication by introducing mutations in the adenoviral genome. Importantly, we also demonstrated that adenoviruses can, at least partially, antagonize A3B by decreasing A3B protein amount and/or A3B enzymatic activity. Results: Our first objective is to examine whether adenoviral infection leads to A3B degradation and, if so, to understand the underlying mechanisms. The viral proteins E1B-55k and E4orf6 are well-known for forming E3-ubiquitin ligase complexes responsible for degrading specific cellular substrates. Initially, we investigate the potential impact of these two viral proteins on the A3B protein level and on its half-life. Additionally, we analysed the involvement of the cullin RING ligase complex. We also explore the possibility of A3B inhibition at the transcriptional level. Finally, based on results obtained from the proximity-dependent biotinylation and MS analysis, we proceed to study the interaction between A3B and the three minor capsid proteins—IIIa, VI, and VIII. This potential interaction is analysed using the Gaussia Complementation Princeps Assay (GPCA). Conclusions and perspectives: We observed that E4orf6 or E1B-55k has no discernible impact on A3B half-life, disproving our first working hypothesis. Furthermore, we provide evidence suggesting that the decrease in A3B protein levels observed during adenoviral infection is likely not attributed to proteasomal degradation or transcriptional inhibition. Our analysis of the interaction between A3B and IIIa, VI, and VIII did not yield definitive results. Further experiments using complementary approaches would be necessary to assess the subcellular localisations and potential interactions between A3B and the capsid minor proteins.

la date de réponse	15 janv. 2024
langue originale	Anglais
L'institution diplômante	Universite de Namur
Superviseur	Nicolas Gillet (Promoteur)